Stage 9: Telegram integration (connector side-service, Mini App, out-of-app push)

New platform/telegram connector (own container, bot token only there):
- go-telegram/bot long-poll loop: /start deep-links + Mini App launch button.
- gRPC API pkg/proto/telegram/v1 (Telegram service): ValidateInitData, Notify
  (renders a localized message + deep-link button), SendToUser/SendToGameChannel
  (admin, wired in Stage 10). Generic methods are platform-agnostic (external_id).
- Bot API base override for Telegram's test environment; Dockerfile + compose
  (VPN sidecar, no public ingress); README.

Gateway:
- initData validation relocated from the gateway into the connector; the gateway
  calls ValidateInitData over gRPC (GATEWAY_CONNECTOR_ADDR), drops the bot token,
  and deletes internal/auth.
- Out-of-app push: runPushPump routes events whose recipient has no live in-app
  stream to connector.Notify, gated by /internal/push-target + the in-app-only
  flag (race-free de-dup); HasSubscribers added to the push hub.

Backend:
- Migration 00007 accounts.notifications_in_app_only (default true) + jetgen.
- ProvisionTelegram seeds a new account's language/display name from the launch
  fields; IdentityExternalID reverse lookup; /internal/push-target handler.

UI:
- Telegram Mini App launch: detect initData, apply themeParams, authTelegram,
  route the deep-link start_param (g/i/f); /telegram/ guard redirects outside
  Telegram. Vite relative base + telegram-web-app.js. In-app-only profile toggle;
  share-to-Telegram link for a friend code. Vitest + Playwright coverage.

Wire/docs/CI: fbs Profile/UpdateProfileRequest gain notifications_in_app_only
(Go + TS); go.work uses ./platform/telegram; go-unit.yaml covers it; PLAN,
ARCHITECTURE, FUNCTIONAL (+ru), UI_DESIGN, READMEs updated.

backend/internal/account/account.go

@@ -10,7 +10,9 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
+	"strings"
 	"time"
+	"unicode/utf8"
 
 	"github.com/go-jet/jet/v2/postgres"
 	"github.com/go-jet/jet/v2/qrm"
@@ -56,9 +58,13 @@ type Account struct {
 	BlockFriendRequests bool
 	// IsGuest marks an ephemeral guest account: a durable row with no identity,
 	// excluded from statistics, friends and history.
-	IsGuest   bool
-	CreatedAt time.Time
-	UpdatedAt time.Time
+	IsGuest bool
+	// NotificationsInAppOnly confines notifications to the in-app live stream when
+	// true (the default): the platform side-service skips out-of-app push for the
+	// account (Stage 9).
+	NotificationsInAppOnly bool
+	CreatedAt              time.Time
+	UpdatedAt              time.Time
 }
 
 // Store is the Postgres-backed query surface for accounts and identities.
@@ -77,6 +83,22 @@ func NewStore(db *sql.DB) *Store {
 // resolved by re-reading the winner's account. A platform identity is recorded
 // as confirmed; an email identity starts unconfirmed.
 func (s *Store) ProvisionByIdentity(ctx context.Context, kind, externalID string) (Account, error) {
+	return s.provision(ctx, kind, externalID, provisionSeed{})
+}
+
+// ProvisionTelegram provisions (or finds) the account bound to a Telegram
+// identity. On first contact only, it seeds the new account's preferred language
+// from the Telegram client languageCode (when it maps to a supported language) and
+// its display name from firstName (falling back to username); an already-existing
+// account is returned unchanged, so a later profile edit is never overwritten.
+func (s *Store) ProvisionTelegram(ctx context.Context, externalID, languageCode, username, firstName string) (Account, error) {
+	return s.provision(ctx, KindTelegram, externalID, telegramSeed(languageCode, username, firstName))
+}
+
+// provision finds the account for (kind, externalID) or creates it with seed,
+// collapsing a concurrent-create race on the identity unique constraint into a
+// re-read of the winner's account.
+func (s *Store) provision(ctx context.Context, kind, externalID string, seed provisionSeed) (Account, error) {
 	acc, err := s.findByIdentity(ctx, kind, externalID)
 	if err == nil {
 		return acc, nil
@@ -85,7 +107,7 @@ func (s *Store) ProvisionByIdentity(ctx context.Context, kind, externalID string
 		return Account{}, err
 	}
 
-	acc, err = s.create(ctx, kind, externalID)
+	acc, err = s.create(ctx, kind, externalID, seed)
 	if err != nil {
 		if isUniqueViolation(err) {
 			// A concurrent caller created the identity first; return theirs.
@@ -96,6 +118,35 @@ func (s *Store) ProvisionByIdentity(ctx context.Context, kind, externalID string
 	return acc, nil
 }
 
+// provisionSeed carries the optional create-time profile seed for a brand-new
+// account (Telegram first contact). Empty fields fall back to the accounts table
+// defaults, so an unknown language keeps the 'en' default and an empty name keeps
+// the ” default.
+type provisionSeed struct {
+	preferredLanguage string
+	displayName       string
+}
+
+// telegramSeed derives the create-time seed from Telegram launch fields: a
+// supported preferred language from languageCode (an ISO-639 code, possibly
+// region-tagged like "ru-RU"), and a display name from firstName or, failing that,
+// username (capped to maxDisplayName runes).
+func telegramSeed(languageCode, username, firstName string) provisionSeed {
+	var seed provisionSeed
+	if lang, _, _ := strings.Cut(strings.ToLower(strings.TrimSpace(languageCode)), "-"); lang == "en" || lang == "ru" {
+		seed.preferredLanguage = lang
+	}
+	name := strings.TrimSpace(firstName)
+	if name == "" {
+		name = strings.TrimSpace(username)
+	}
+	if utf8.RuneCountInString(name) > maxDisplayName {
+		name = string([]rune(name)[:maxDisplayName])
+	}
+	seed.displayName = name
+	return seed
+}
+
 // GetByID loads the account identified by id, or ErrNotFound when it is absent.
 func (s *Store) GetByID(ctx context.Context, id uuid.UUID) (Account, error) {
 	stmt := postgres.SELECT(table.Accounts.AllColumns).
@@ -113,6 +164,29 @@ func (s *Store) GetByID(ctx context.Context, id uuid.UUID) (Account, error) {
 	return modelToAccount(row), nil
 }
 
+// IdentityExternalID returns the external_id of the account's identity of the
+// given kind, or ErrNotFound when the account has no such identity. The Telegram
+// side-service uses it (through the gateway push-target lookup) to address an
+// out-of-app notification to a recipient's Telegram chat.
+func (s *Store) IdentityExternalID(ctx context.Context, accountID uuid.UUID, kind string) (string, error) {
+	stmt := postgres.SELECT(table.Identities.ExternalID).
+		FROM(table.Identities).
+		WHERE(
+			table.Identities.AccountID.EQ(postgres.UUID(accountID)).
+				AND(table.Identities.Kind.EQ(postgres.String(kind))),
+		).
+		LIMIT(1)
+
+	var row model.Identities
+	if err := stmt.QueryContext(ctx, s.db, &row); err != nil {
+		if errors.Is(err, qrm.ErrNoRows) {
+			return "", ErrNotFound
+		}
+		return "", fmt.Errorf("account: identity external id (%s, %s): %w", accountID, kind, err)
+	}
+	return row.ExternalID, nil
+}
+
 // findByIdentity joins identities to accounts and returns the matching account,
 // or ErrNotFound.
 func (s *Store) findByIdentity(ctx context.Context, kind, externalID string) (Account, error) {
@@ -137,9 +211,9 @@ func (s *Store) findByIdentity(ctx context.Context, kind, externalID string) (Ac
 	return modelToAccount(row), nil
 }
 
-// create inserts a new account and its first identity inside one transaction
-// and returns the persisted account row.
-func (s *Store) create(ctx context.Context, kind, externalID string) (Account, error) {
+// create inserts a new account (seeded from seed) and its first identity inside
+// one transaction and returns the persisted account row.
+func (s *Store) create(ctx context.Context, kind, externalID string, seed provisionSeed) (Account, error) {
 	accountID, err := uuid.NewV7()
 	if err != nil {
 		return Account{}, fmt.Errorf("account: new account id: %w", err)
@@ -151,9 +225,16 @@ func (s *Store) create(ctx context.Context, kind, externalID string) (Account, e
 
 	var created Account
 	err = withTx(ctx, s.db, func(tx *sql.Tx) error {
+		// Seed the new row's display name and language (Telegram first contact); an
+		// empty seed reproduces the table defaults ('' and 'en') the other callers
+		// relied on, so their behaviour is unchanged.
+		lang := seed.preferredLanguage
+		if lang == "" {
+			lang = "en"
+		}
 		insertAccount := table.Accounts.
-			INSERT(table.Accounts.AccountID).
-			VALUES(accountID).
+			INSERT(table.Accounts.AccountID, table.Accounts.DisplayName, table.Accounts.PreferredLanguage).
+			VALUES(accountID, seed.displayName, lang).
 			RETURNING(table.Accounts.AllColumns)
 
 		var row model.Accounts
@@ -230,18 +311,19 @@ func (s *Store) SpendHint(ctx context.Context, id uuid.UUID) (bool, error) {
 // modelToAccount projects a generated model row into the public Account struct.
 func modelToAccount(row model.Accounts) Account {
 	return Account{
-		ID:                  row.AccountID,
-		DisplayName:         row.DisplayName,
-		PreferredLanguage:   row.PreferredLanguage,
-		TimeZone:            row.TimeZone,
-		AwayStart:           row.AwayStart,
-		AwayEnd:             row.AwayEnd,
-		HintBalance:         int(row.HintBalance),
-		BlockChat:           row.BlockChat,
-		BlockFriendRequests: row.BlockFriendRequests,
-		IsGuest:             row.IsGuest,
-		CreatedAt:           row.CreatedAt,
-		UpdatedAt:           row.UpdatedAt,
+		ID:                     row.AccountID,
+		DisplayName:            row.DisplayName,
+		PreferredLanguage:      row.PreferredLanguage,
+		TimeZone:               row.TimeZone,
+		AwayStart:              row.AwayStart,
+		AwayEnd:                row.AwayEnd,
+		HintBalance:            int(row.HintBalance),
+		BlockChat:              row.BlockChat,
+		BlockFriendRequests:    row.BlockFriendRequests,
+		IsGuest:                row.IsGuest,
+		NotificationsInAppOnly: row.NotificationsInAppOnly,
+		CreatedAt:              row.CreatedAt,
+		UpdatedAt:              row.UpdatedAt,
 	}
 }