feat(payments): per-channel Robokassa shops on the direct rail

Split the single Robokassa direct rail into one merchant shop per channel
(web / android; ios later), chosen by the trusted X-Platform subtype, while
every shop still credits the one `direct` wallet — merchant-account separation
for accounting and receipts, not a new wallet.

- config: a channel-keyed shops registry (web seeds from the legacy vars or
  _WEB_*, android from _ANDROID_*); an empty shop leaves the rail dormant;
  per-shop validation.
- intake: the order picks its shop by subtype (unknown falls back to web); the
  per-shop Result callback is verified by that shop's own Password2 at
  /pay/robokassa/result/<channel> (the gateway extracts the channel; Caddy's
  /pay/* glob already forwards it — no Caddyfile change).
- persistence: an additive `shop` column on the order (migration 00015),
  recorded from the payment context, surfaced per entry in the admin report.
- standalone apps sign in by email only, so a direct purchase keeps its email
  anchor.
- docs: PAYMENTS (+ru) topology, deploy env vars + compose mapping, the
  decisions log (D41 revised for the ИП / 54-ФЗ move; D42-D44), the plan.

Contour-safe: dormant until shops are configured; the migration is additive
(no wipe); no client wire change. Fiscalization (Receipt/Email) and the gateway
`direct/android` subtype follow when the ИП / RuStore are live.

backend/internal/adminconsole/templates/pages/user_detail.gohtml

@@ -76,10 +76,10 @@
 {{$uid := .ID}}
 {{if .Finance.Ledger}}
 <table class="list">
-<thead><tr><th>Time</th><th>Kind</th><th>Source</th><th>Origin</th><th>Chips</th><th>Order</th><th>Provider</th><th>Detail</th><th></th></tr></thead>
+<thead><tr><th>Time</th><th>Kind</th><th>Source</th><th>Origin</th><th>Chips</th><th>Order</th><th>Provider</th><th>Shop</th><th>Detail</th><th></th></tr></thead>
 <tbody>
 {{range .Finance.Ledger}}
-<tr><td>{{.At}}</td><td>{{.Kind}}</td><td>{{.Source}}</td><td>{{.Origin}}</td><td>{{.ChipsDelta}}</td><td>{{if .Order}}<code>{{.Order}}</code>{{end}}</td><td>{{.Provider}}</td><td>{{if .Snapshot}}<code>{{.Snapshot}}</code>{{end}}</td>
+<tr><td>{{.At}}</td><td>{{.Kind}}</td><td>{{.Source}}</td><td>{{.Origin}}</td><td>{{.ChipsDelta}}</td><td>{{if .Order}}<code>{{.Order}}</code>{{end}}</td><td>{{.Provider}}</td><td>{{.Shop}}</td><td>{{if .Snapshot}}<code>{{.Snapshot}}</code>{{end}}</td>
 <td>{{if and (eq .Kind "fund") .Order}}<form class="form" method="post" action="/_gm/users/{{$uid}}/refund" onsubmit="return confirm('Refund this order in full? Record the money refund on the rail first; this revokes the chips (floored at 0).')"><input type="hidden" name="order_id" value="{{.Order}}"><button type="submit">Refund</button></form>{{end}}</td></tr>
 {{end}}
 </tbody>

backend/internal/adminconsole/views.go

@@ -232,8 +232,8 @@ type BenefitRow struct {
 }
 
 // LedgerRow is one append-only ledger entry: its kind, funding source / benefit origin, signed chip
-// delta, the product / order / provider it references (empty when none), the raw snapshot JSON and
-// the pre-formatted time.
+// delta, the product / order / provider / direct-rail shop it references (empty when none), the raw
+// snapshot JSON and the pre-formatted time.
 type LedgerRow struct {
 	Kind       string
 	Source     string
@@ -242,6 +242,7 @@ type LedgerRow struct {
 	Product    string
 	Order      string
 	Provider   string
+	Shop       string
 	Snapshot   string
 	At         string
 }

backend/internal/config/config.go

@@ -65,9 +65,9 @@ type Config struct {
 	// RendererURL is the base URL of the internal image-render sidecar (e.g.
 	// http://renderer:8090). Empty disables the PNG export artifact.
 	RendererURL string
-	// Robokassa configures the direct-rail (RUB) payment provider. An empty MerchantLogin
-	// leaves the direct order and Result-callback endpoints unregistered.
-	Robokassa robokassa.Config
+	// Robokassa configures the direct-rail (RUB) payment provider — one merchant shop per channel
+	// (D42). An empty set leaves the direct order and Result-callback endpoints unregistered.
+	Robokassa robokassa.Shops
 }
 
 // Defaults applied when the corresponding environment variable is unset.
@@ -157,11 +157,19 @@ func Load() (Config, error) {
 		AdminTo:   os.Getenv("BACKEND_ADMIN_EMAIL"),
 	}
 
-	robo := robokassa.Config{
-		MerchantLogin: os.Getenv("BACKEND_ROBOKASSA_MERCHANT_LOGIN"),
-		Password1:     os.Getenv("BACKEND_ROBOKASSA_PASSWORD1"),
-		Password2:     os.Getenv("BACKEND_ROBOKASSA_PASSWORD2"),
-		IsTest:        os.Getenv("BACKEND_ROBOKASSA_TEST") == "1",
+	// Robokassa direct rail: one merchant shop per channel (D42). The legacy single-shop vars seed
+	// the web channel so existing deploys keep working; the per-channel vars add the rest. A shop
+	// with no MerchantLogin is dropped (the rail stays dormant when none is configured).
+	shops := robokassa.Shops{}
+	web := robokassaShop("BACKEND_ROBOKASSA_WEB")
+	if web.MerchantLogin == "" {
+		web = robokassaShop("BACKEND_ROBOKASSA") // legacy single-shop credentials seed the web channel
+	}
+	if web.MerchantLogin != "" {
+		shops[robokassa.ChannelWeb] = web
+	}
+	if android := robokassaShop("BACKEND_ROBOKASSA_ANDROID"); android.MerchantLogin != "" {
+		shops[robokassa.ChannelAndroid] = android
 	}
 
 	c := Config{
@@ -181,7 +189,7 @@ func Load() (Config, error) {
 		GuestRetention:    guestRetention,
 		ExportSignKey:     os.Getenv("BACKEND_EXPORT_SIGN_KEY"),
 		RendererURL:       os.Getenv("BACKEND_RENDERER_URL"),
-		Robokassa:         robo,
+		Robokassa:         shops,
 	}
 	if err := c.validate(); err != nil {
 		return Config{}, err
@@ -234,8 +242,10 @@ func (c Config) validate() error {
 			return fmt.Errorf("config: BACKEND_PUBLIC_BASE_URL %q must be an absolute URL (scheme://host)", c.PublicBaseURL)
 		}
 	}
-	if c.Robokassa.MerchantLogin != "" && (c.Robokassa.Password1 == "" || c.Robokassa.Password2 == "") {
-		return fmt.Errorf("config: BACKEND_ROBOKASSA_PASSWORD1 and BACKEND_ROBOKASSA_PASSWORD2 must be set when BACKEND_ROBOKASSA_MERCHANT_LOGIN is")
+	for channel, shop := range c.Robokassa {
+		if shop.Password1 == "" || shop.Password2 == "" {
+			return fmt.Errorf("config: robokassa shop %q: password1 and password2 must be set when its merchant login is", channel)
+		}
 	}
 	return nil
 }
@@ -276,3 +286,15 @@ func envDuration(key string, fallback time.Duration) (time.Duration, error) {
 	}
 	return d, nil
 }
+
+// robokassaShop reads a Robokassa shop's four credentials from the environment under prefix (e.g.
+// "BACKEND_ROBOKASSA_WEB" → _MERCHANT_LOGIN / _PASSWORD1 / _PASSWORD2 / _TEST). A missing
+// MerchantLogin yields a zero Config the caller drops.
+func robokassaShop(prefix string) robokassa.Config {
+	return robokassa.Config{
+		MerchantLogin: os.Getenv(prefix + "_MERCHANT_LOGIN"),
+		Password1:     os.Getenv(prefix + "_PASSWORD1"),
+		Password2:     os.Getenv(prefix + "_PASSWORD2"),
+		IsTest:        os.Getenv(prefix+"_TEST") == "1",
+	}
+}

backend/internal/payments/service_intake.go

@@ -46,6 +46,7 @@ func (s *Service) CreateOrder(ctx context.Context, accountID uuid.UUID, cxt Cont
 		amount:    pack.price,
 		origin:    method,
 		provider:  provider,
+		shop:      directShop(cxt),
 	}
 	if err := s.store.createOrder(ctx, o, s.clock()); err != nil {
 		return OrderResult{}, err
@@ -53,6 +54,16 @@ func (s *Service) CreateOrder(ctx context.Context, accountID uuid.UUID, cxt Cont
 	return OrderResult{OrderID: orderID, Amount: pack.price, Title: pack.title}, nil
 }
 
+// directShop returns the merchant shop (channel) a direct order is issued through — the trusted
+// platform subtype for the direct rail ("web"/"android"), or "" for any other rail (the per-shop
+// split is direct-only; D42/D44). Recorded on the order for the admin per-channel breakdown.
+func directShop(cxt Context) string {
+	if cxt.Kind == SourceDirect {
+		return cxt.Subtype
+	}
+	return ""
+}
+
 // OrderItem returns a pending order's human title and the amount it charges, in the order's own
 // currency — the details a provider's item-lookup phase needs (VK's get_item). It reads the order
 // and the pack title, honouring the pack even if it was later deactivated (mirrors Fund).

backend/internal/payments/statement.go

@@ -42,7 +42,8 @@ type RiskInfo struct {
 }
 
 // LedgerEntry is one append-only ledger row projected for the report. The string ids are empty when
-// the column is NULL; Snapshot is the raw purchase/refund JSON (empty when none).
+// the column is NULL; Shop is the direct-rail merchant channel the referenced order used (empty for
+// other rails or order-less rows); Snapshot is the raw purchase/refund JSON (empty when none).
 type LedgerEntry struct {
 	Kind              string
 	Source            string
@@ -52,6 +53,7 @@ type LedgerEntry struct {
 	OrderID           string
 	Provider          string
 	ProviderPaymentID string
+	Shop              string
 	Snapshot          string
 	CreatedAt         time.Time
 }

backend/internal/payments/store_intake.go

@@ -151,6 +151,7 @@ type newOrder struct {
 	amount    Money
 	origin    Source
 	provider  string
+	shop      string
 }
 
 // createOrder inserts a pending order.
@@ -159,12 +160,12 @@ func (s *Store) createOrder(ctx context.Context, o newOrder, now time.Time) erro
 		table.Orders.OrderID, table.Orders.AccountID, table.Orders.Platform,
 		table.Orders.ProductID, table.Orders.ExpectedAmount, table.Orders.Currency,
 		table.Orders.Origin, table.Orders.Status, table.Orders.Provider,
-		table.Orders.CreatedAt, table.Orders.UpdatedAt,
+		table.Orders.CreatedAt, table.Orders.UpdatedAt, table.Orders.Shop,
 	).VALUES(
 		o.orderID, o.accountID, o.platform,
 		o.productID, o.amount.Minor(), string(o.amount.Currency()),
 		string(o.origin), "pending", o.provider,
-		now, now,
+		now, now, o.shop,
 	)
 	if _, err := stmt.ExecContext(ctx, s.db); err != nil {
 		return fmt.Errorf("payments: create order: %w", err)

backend/internal/payments/store_statement.go

@@ -74,9 +74,39 @@ func (s *Store) accountStatement(ctx context.Context, accountID uuid.UUID) (Stat
 			CreatedAt:         r.CreatedAt,
 		})
 	}
+
+	// Annotate direct-rail entries with the merchant shop (channel) their order was issued through
+	// (E10/D44), keyed by the ledger's order id. Non-direct / order-less entries stay "".
+	shops, err := s.orderShops(ctx, accountID)
+	if err != nil {
+		return Statement{}, err
+	}
+	for i := range out.Ledger {
+		out.Ledger[i].Shop = shops[out.Ledger[i].OrderID]
+	}
 	return out, nil
 }
 
+// orderShops maps an account's order ids (as strings) to the merchant shop (channel) each direct
+// order was issued through, for annotating the ledger report (E10/D44). Orders with an empty shop
+// (non-direct or pre-split) are omitted, so a lookup miss yields "".
+func (s *Store) orderShops(ctx context.Context, accountID uuid.UUID) (map[string]string, error) {
+	var rows []model.Orders
+	if err := postgres.SELECT(table.Orders.OrderID, table.Orders.Shop).
+		FROM(table.Orders).
+		WHERE(table.Orders.AccountID.EQ(postgres.UUID(accountID))).
+		QueryContext(ctx, s.db, &rows); err != nil {
+		return nil, fmt.Errorf("payments: load order shops %s: %w", accountID, err)
+	}
+	m := make(map[string]string, len(rows))
+	for _, r := range rows {
+		if r.Shop != "" {
+			m[r.OrderID.String()] = r.Shop
+		}
+	}
+	return m, nil
+}
+
 // allLedger reads the entire append-only ledger (all accounts, newest first) for the admin export.
 func (s *Store) allLedger(ctx context.Context) ([]LedgerExportRow, error) {
 	var rows []model.Ledger

backend/internal/postgres/jet/payments/model/orders.go

@@ -25,4 +25,5 @@ type Orders struct {
 	ProviderPaymentID *string
 	CreatedAt         time.Time
 	UpdatedAt         time.Time
+	Shop              string
 }

backend/internal/postgres/jet/payments/table/orders.go

@@ -29,6 +29,7 @@ type ordersTable struct {
 	ProviderPaymentID postgres.ColumnString
 	CreatedAt         postgres.ColumnTimestampz
 	UpdatedAt         postgres.ColumnTimestampz
+	Shop              postgres.ColumnString
 
 	AllColumns     postgres.ColumnList
 	MutableColumns postgres.ColumnList
@@ -82,9 +83,10 @@ func newOrdersTableImpl(schemaName, tableName, alias string) ordersTable {
 		ProviderPaymentIDColumn = postgres.StringColumn("provider_payment_id")
 		CreatedAtColumn         = postgres.TimestampzColumn("created_at")
 		UpdatedAtColumn         = postgres.TimestampzColumn("updated_at")
-		allColumns              = postgres.ColumnList{OrderIDColumn, AccountIDColumn, PlatformColumn, ProductIDColumn, ExpectedAmountColumn, CurrencyColumn, OriginColumn, StatusColumn, ProviderColumn, ProviderPaymentIDColumn, CreatedAtColumn, UpdatedAtColumn}
-		mutableColumns          = postgres.ColumnList{AccountIDColumn, PlatformColumn, ProductIDColumn, ExpectedAmountColumn, CurrencyColumn, OriginColumn, StatusColumn, ProviderColumn, ProviderPaymentIDColumn, CreatedAtColumn, UpdatedAtColumn}
-		defaultColumns          = postgres.ColumnList{StatusColumn, CreatedAtColumn, UpdatedAtColumn}
+		ShopColumn              = postgres.StringColumn("shop")
+		allColumns              = postgres.ColumnList{OrderIDColumn, AccountIDColumn, PlatformColumn, ProductIDColumn, ExpectedAmountColumn, CurrencyColumn, OriginColumn, StatusColumn, ProviderColumn, ProviderPaymentIDColumn, CreatedAtColumn, UpdatedAtColumn, ShopColumn}
+		mutableColumns          = postgres.ColumnList{AccountIDColumn, PlatformColumn, ProductIDColumn, ExpectedAmountColumn, CurrencyColumn, OriginColumn, StatusColumn, ProviderColumn, ProviderPaymentIDColumn, CreatedAtColumn, UpdatedAtColumn, ShopColumn}
+		defaultColumns          = postgres.ColumnList{StatusColumn, CreatedAtColumn, UpdatedAtColumn, ShopColumn}
 	)
 
 	return ordersTable{
@@ -103,6 +105,7 @@ func newOrdersTableImpl(schemaName, tableName, alias string) ordersTable {
 		ProviderPaymentID: ProviderPaymentIDColumn,
 		CreatedAt:         CreatedAtColumn,
 		UpdatedAt:         UpdatedAtColumn,
+		Shop:              ShopColumn,
 
 		AllColumns:     allColumns,
 		MutableColumns: mutableColumns,

backend/internal/postgres/migrations/00015_orders_shop.sql

@@ -0,0 +1,13 @@
+-- Multi-shop direct rail (E10/D44): record which Robokassa merchant shop (channel) issued a direct
+-- order — "web" / "android" (ios later) — so the admin financial report can break direct payments
+-- down by channel. Only the direct rail is per-channel; other rails leave it "". Additive only (a
+-- defaulted column), applies forward via goose with no data rewrite (no contour wipe); an image
+-- rollback ignores the column.
+-- +goose Up
+
+ALTER TABLE payments.orders
+    ADD COLUMN shop text NOT NULL DEFAULT '';
+
+-- +goose Down
+
+ALTER TABLE payments.orders DROP COLUMN shop;

backend/internal/robokassa/shops.go

@@ -0,0 +1,54 @@
+package robokassa
+
+// Shops is a set of Robokassa merchant shops keyed by channel — the subtype of the trusted
+// X-Platform signal for the direct rail ("web", "android"; "ios" later). The direct rail routes a
+// payment to the per-channel shop for separate merchant accounts, accounting and receipts, while
+// every shop still credits the one direct wallet (docs/PAYMENTS_DECISIONS_ru.md D42). An empty set
+// leaves the direct order and Result-callback endpoints unregistered.
+type Shops map[string]Config
+
+// Channel constants name the direct-rail X-Platform subtypes a shop is keyed by. ChannelWeb is the
+// default: an unknown or empty channel routes here on the order side, and the legacy single-shop
+// configuration seeds it.
+const (
+	ChannelWeb     = "web"
+	ChannelAndroid = "android"
+)
+
+// Shop returns the shop that issues an order for channel, falling back to the web shop when channel
+// is unknown, empty or not configured. The fallback is safe: routing only chooses the merchant
+// account and receipt, never the credited wallet (always direct, D42), so a mis-attributed channel
+// costs at most accounting accuracy, not money. The second result is false when neither the channel
+// nor the web shop has a merchant login (the rail is unconfigured).
+func (s Shops) Shop(channel string) (Config, bool) {
+	if channel != "" {
+		if c, ok := s[channel]; ok && c.MerchantLogin != "" {
+			return c, true
+		}
+	}
+	if c, ok := s[ChannelWeb]; ok && c.MerchantLogin != "" {
+		return c, true
+	}
+	return Config{}, false
+}
+
+// Verifier returns the shop whose Password2 verifies a Result callback delivered to channel's
+// dedicated Result route. Unlike Shop it does not fall back to web: each shop's callback is verified
+// only by that shop's own credentials, so a route with no configured shop reports false (and its
+// handler answers as unregistered). The second result is false when channel has no merchant login.
+func (s Shops) Verifier(channel string) (Config, bool) {
+	if c, ok := s[channel]; ok && c.MerchantLogin != "" {
+		return c, true
+	}
+	return Config{}, false
+}
+
+// Configured reports whether at least one shop has a merchant login (the direct rail is live).
+func (s Shops) Configured() bool {
+	for _, c := range s {
+		if c.MerchantLogin != "" {
+			return true
+		}
+	}
+	return false
+}

backend/internal/robokassa/shops_test.go

@@ -0,0 +1,52 @@
+package robokassa
+
+import "testing"
+
+func TestShopsShopRouting(t *testing.T) {
+	shops := Shops{
+		ChannelWeb:     {MerchantLogin: "webshop", Password1: "w1", Password2: "w2"},
+		ChannelAndroid: {MerchantLogin: "androidshop", Password1: "a1", Password2: "a2"},
+	}
+	// Order side: the exact channel wins.
+	if c, ok := shops.Shop(ChannelAndroid); !ok || c.MerchantLogin != "androidshop" {
+		t.Errorf("Shop(android) = %q/%v, want androidshop/true", c.MerchantLogin, ok)
+	}
+	// Order side: an unknown or empty channel falls back to the web shop (safe — always credits direct).
+	if c, ok := shops.Shop("ios"); !ok || c.MerchantLogin != "webshop" {
+		t.Errorf("Shop(ios) = %q/%v, want webshop/true (web fallback)", c.MerchantLogin, ok)
+	}
+	if c, ok := shops.Shop(""); !ok || c.MerchantLogin != "webshop" {
+		t.Errorf("Shop(empty) = %q/%v, want webshop/true (web fallback)", c.MerchantLogin, ok)
+	}
+	// No web shop and an unknown channel → unconfigured.
+	if _, ok := (Shops{ChannelAndroid: {MerchantLogin: "androidshop", Password1: "a1", Password2: "a2"}}).Shop("ios"); ok {
+		t.Error("Shop(ios) with no web shop returned ok, want false")
+	}
+}
+
+func TestShopsVerifierIsStrict(t *testing.T) {
+	shops := Shops{
+		ChannelWeb:     {MerchantLogin: "webshop", Password1: "w1", Password2: "w2"},
+		ChannelAndroid: {MerchantLogin: "androidshop", Password1: "a1", Password2: "a2"},
+	}
+	// Callback side: the exact channel's own credentials, no web fallback (each callback is verified
+	// only by its own shop's Password2).
+	if c, ok := shops.Verifier(ChannelAndroid); !ok || c.MerchantLogin != "androidshop" {
+		t.Errorf("Verifier(android) = %q/%v, want androidshop/true", c.MerchantLogin, ok)
+	}
+	if _, ok := shops.Verifier("ios"); ok {
+		t.Error("Verifier(ios) returned ok, want false (no fallback)")
+	}
+}
+
+func TestShopsConfigured(t *testing.T) {
+	if (Shops{}).Configured() {
+		t.Error("an empty set reported configured")
+	}
+	if (Shops{ChannelWeb: {}}).Configured() {
+		t.Error("a shop with no merchant login reported configured")
+	}
+	if !(Shops{ChannelWeb: {MerchantLogin: "s", Password1: "1", Password2: "2"}}).Configured() {
+		t.Error("a configured shop reported not configured")
+	}
+}

backend/internal/server/handlers.go

@@ -89,7 +89,7 @@ func (s *Server) registerRoutes() {
 		// payment over the reverse bot-link; the gateway proxies both onto these gateway-only routes.
 		s.internal.POST("/payments/telegram/precheckout", s.handleTelegramPreCheckout)
 		s.internal.POST("/payments/telegram/payment", s.handleTelegramPayment)
-		if s.robokassa.MerchantLogin != "" {
+		if s.robokassa.Configured() {
 			s.internal.POST("/payments/robokassa/result", s.handleRobokassaResult)
 		}
 	}

backend/internal/server/handlers_admin_console.go

@@ -482,7 +482,7 @@ func financeView(stmt payments.Statement) adminconsole.FinanceView {
 	for _, e := range stmt.Ledger {
 		fv.Ledger = append(fv.Ledger, adminconsole.LedgerRow{
 			Kind: e.Kind, Source: e.Source, Origin: e.Origin, ChipsDelta: e.ChipsDelta,
-			Product: e.ProductID, Order: e.OrderID, Provider: e.Provider, Snapshot: e.Snapshot,
+			Product: e.ProductID, Order: e.OrderID, Provider: e.Provider, Shop: e.Shop, Snapshot: e.Snapshot,
 			At: fmtTime(e.CreatedAt),
 		})
 	}

backend/internal/server/handlers_intake.go

@@ -12,6 +12,7 @@ import (
 	"go.uber.org/zap"
 
 	"scrabble/backend/internal/payments"
+	"scrabble/backend/internal/robokassa"
 )
 
 // Ledger/order provider tags per rail.
@@ -68,7 +69,8 @@ func (s *Server) handleWalletOrder(c *gin.Context) {
 	}
 	switch cxt.Kind {
 	case payments.SourceDirect:
-		if s.robokassa.MerchantLogin == "" {
+		shop, ok := s.robokassa.Shop(cxt.Subtype)
+		if !ok {
 			c.AbortWithStatusJSON(http.StatusNotImplemented, errorResponse{Error: errorBody{Code: "rail_unavailable", Message: "this payment method is not available"}})
 			return
 		}
@@ -89,7 +91,7 @@ func (s *Server) handleWalletOrder(c *gin.Context) {
 		}
 		c.JSON(http.StatusOK, walletOrderResponse{
 			OrderID:     res.OrderID.String(),
-			RedirectURL: s.robokassa.PaymentURL(res.OrderID, res.Amount.Major(), res.Title),
+			RedirectURL: shop.PaymentURL(res.OrderID, res.Amount.Major(), res.Title),
 			Rail:        providerRobokassa,
 		})
 	case payments.SourceVK:
@@ -136,7 +138,16 @@ func (s *Server) handleRobokassaResult(c *gin.Context) {
 	for k, val := range params {
 		v.Set(k, val)
 	}
-	orderID, outSum, ok := s.robokassa.VerifyResult(v)
+	// The per-shop Result route carries the channel as ?channel=; the legacy bare route defaults to
+	// the web shop. Each channel is verified only by its own shop's Password2 (Verifier is strict).
+	channel := c.DefaultQuery("channel", robokassa.ChannelWeb)
+	shop, ok := s.robokassa.Verifier(channel)
+	if !ok {
+		s.log.Warn("robokassa result: unknown shop channel", zap.String("channel", channel))
+		c.String(http.StatusBadRequest, "bad sign")
+		return
+	}
+	orderID, outSum, ok := shop.VerifyResult(v)
 	if !ok {
 		s.log.Warn("robokassa result: bad signature")
 		c.String(http.StatusBadRequest, "bad sign")

backend/internal/server/server.go

@@ -115,9 +115,9 @@ type Deps struct {
 	// Renderer is the image-render sidecar client for the PNG export artifact. A
 	// nil Renderer makes the PNG download answer 404 (the GCG artifact still works).
 	Renderer *render.Client
-	// Robokassa configures the direct-rail (RUB) provider; an empty MerchantLogin leaves the
-	// order and Result-callback endpoints unregistered.
-	Robokassa robokassa.Config
+	// Robokassa configures the direct-rail (RUB) provider — one merchant shop per channel; an empty
+	// set leaves the order and Result-callback endpoints unregistered.
+	Robokassa robokassa.Shops
 }
 
 // Server owns the gin engine, the underlying HTTP server and the readiness
@@ -146,7 +146,7 @@ type Server struct {
 	ads         *ads.Service
 	payments    *payments.Service
 	gamelimits  *gamelimits.Service
-	robokassa   robokassa.Config
+	robokassa   robokassa.Shops
 	notifier    notify.Publisher
 	console     *adminconsole.Renderer
 	exportKey   []byte