feat(ads): VK post-move interstitial + retire deprecated hint_balance/paid_account

Interstitial video after a confirmed play or a hint, VK-only, offline
banner-only. The gate is client-mirrored: the backend puts the config
cooldowns (global 5m / vs_ai 30m / hint 1m) and a suppressed flag (the
no-ads / no_banner gate, same as the banner) on Profile.ads via adsFor;
the client self-gates on a per-kind last-shown time in localStorage, with
the VITE_ADS_STUB contour "ad fired" toast. Never fires after a pass,
exchange or resign. maybeShowInterstitial + vkShowInterstitial; the codec
and gateway transcode carry the ads block.

Also retires the deprecated accounts.hint_balance / paid_account domain
usage (expand-contract, code only — the columns stay for a later DROP so
image rollback stays DB-safe): drop the Account fields and their scan, the
dead account.SpendHint, account.GrantHints and the admin grant-hints
action; the in-game hint display now comes wholly from the payments hint
benefit. Banner eligibility and account merge no longer read the legacy
flags.

Tests: ads.test.ts (the client-mirrored gate), the codec ads round-trip,
the gateway ads transcode test, and a profile ads-config integration test
(cooldowns + suppressed under no-ads / no_banner). Docs: PAYMENTS §10 (+ru)
interstitial, the decision amends, backend README, the plan.

backend/internal/server/banner.go

@@ -57,9 +57,9 @@ type bannerTimingsDTO struct {
 func (s *Server) profileResponse(ctx context.Context, acc account.Account) profileResponse {
 	r := profileResponseFor(acc)
 	// Resolve the payments gate once (execution context + present sources) and feed it to both
-	// the hint count and the banner. The profile hint balance now comes from the payments benefit
-	// (context-aware), not the deprecated accounts.hint_balance column; on any failure the legacy
-	// value from profileResponseFor (zeroed in production) stands.
+	// the hint count and the banner. The profile hint balance comes from the payments benefit
+	// (context-aware); the deprecated accounts.hint_balance column is no longer read, so on any
+	// failure the fallback from profileResponseFor is a plain 0.
 	cxt, present, err := s.walletGate(ctx, acc.ID)
 	if err != nil {
 		s.log.Warn("profile: wallet gate failed", zap.String("account", acc.ID.String()), zap.Error(err))
@@ -71,6 +71,7 @@ func (s *Server) profileResponse(ctx context.Context, acc account.Account) profi
 		}
 	}
 	r.Banner = s.bannerFor(ctx, acc, cxt, present)
+	r.Ads = s.adsFor(ctx, acc, cxt, present)
 	s.fillLinkedIdentities(ctx, &r, acc.ID)
 	r.DictVersions = s.currentDictVersions()
 	return r
@@ -177,6 +178,44 @@ func (s *Server) bannerFor(ctx context.Context, acc account.Account, cxt payment
 	}
 }
 
+// adsDTO is the post-move interstitial config in the profile: the client-mirrored cooldowns
+// (seconds) and whether ads are suppressed in the context (a no-ads benefit applicable here, or the
+// no_banner role). The client shows a VK interstitial after a confirmed move / hint only when not
+// suppressed and the mirrored cooldown has elapsed.
+type adsDTO struct {
+	CooldownGlobalS int  `json:"cooldown_global_s"`
+	CooldownVsAiS   int  `json:"cooldown_vs_ai_s"`
+	CooldownHintS   int  `json:"cooldown_hint_s"`
+	Suppressed      bool `json:"suppressed"`
+}
+
+// adsFor builds the profile interstitial-ad config: the cooldowns and whether ads are suppressed
+// here (the same no-ads / no_banner gate as the banner). A read failure logs and yields a suppressed
+// block (fail-safe: no interstitial), so the profile still succeeds.
+func (s *Server) adsFor(ctx context.Context, acc account.Account, cxt payments.Context, present []payments.Source) *adsDTO {
+	if s.payments == nil {
+		return nil
+	}
+	global, vsAi, hint, err := s.payments.InterstitialCooldowns(ctx)
+	if err != nil {
+		s.log.Warn("profile: ad cooldowns read failed", zap.String("account", acc.ID.String()), zap.Error(err))
+		return &adsDTO{Suppressed: true}
+	}
+	suppressed := false
+	if adFree, aerr := s.payments.AdFree(ctx, acc.ID, cxt, present); aerr != nil {
+		s.log.Warn("profile: ad-free read failed", zap.String("account", acc.ID.String()), zap.Error(aerr))
+		suppressed = true // fail-safe: suppress the interstitial when eligibility is unknown
+	} else {
+		suppressed = adFree
+	}
+	if !suppressed {
+		if noBanner, berr := s.accounts.HasRole(ctx, acc.ID, account.RoleNoBanner); berr == nil {
+			suppressed = noBanner
+		}
+	}
+	return &adsDTO{CooldownGlobalS: global, CooldownVsAiS: vsAi, CooldownHintS: hint, Suppressed: suppressed}
+}
+
 // bannerCampaignFromActive flattens a resolved campaign into its wire DTO,
 // projecting each optional colour set into its three "#rrggbb" fields (empty when
 // the set is absent, so JSON omitempty drops them).

backend/internal/server/dto.go

@@ -60,6 +60,11 @@ type profileResponse struct {
 	// see the banner (a free account with an empty hint wallet and without the
 	// no_banner role), absent otherwise. See banner.go.
 	Banner *bannerDTO `json:"banner,omitempty"`
+	// Ads carries the post-move interstitial config for the client's client-mirrored gate: the
+	// cooldowns (seconds) and whether ads are suppressed in this context (no-ads / no_banner role).
+	// The client shows a VK interstitial after a confirmed move / hint when not suppressed and the
+	// cooldown has elapsed. Always present (the client also gates VK-only + online itself).
+	Ads *adsDTO `json:"ads,omitempty"`
 	// Email is the account's confirmed email address ("" when none); TelegramLinked and
 	// VkLinked report whether a platform identity is attached. They drive the profile's
 	// link / unlink / change-email controls, and are filled outside the pure projection
@@ -218,13 +223,15 @@ func sessionResponseFor(token string, acc account.Account) sessionResponse {
 // profileResponseFor projects an account into its profile DTO.
 func profileResponseFor(acc account.Account) profileResponse {
 	return profileResponse{
-		UserID:                 acc.ID.String(),
-		DisplayName:            acc.DisplayName,
-		PreferredLanguage:      acc.PreferredLanguage,
-		TimeZone:               acc.TimeZone,
-		AwayStart:              acc.AwayStart.Format(awayTimeLayout),
-		AwayEnd:                acc.AwayEnd.Format(awayTimeLayout),
-		HintBalance:            acc.HintBalance,
+		UserID:            acc.ID.String(),
+		DisplayName:       acc.DisplayName,
+		PreferredLanguage: acc.PreferredLanguage,
+		TimeZone:          acc.TimeZone,
+		AwayStart:         acc.AwayStart.Format(awayTimeLayout),
+		AwayEnd:           acc.AwayEnd.Format(awayTimeLayout),
+		// The hint balance comes from the payments benefit; profileResponse overrides this
+		// with the context-aware count. This zero is the fallback when that read fails.
+		HintBalance:            0,
 		BlockChat:              acc.BlockChat,
 		BlockFriendRequests:    acc.BlockFriendRequests,
 		IsGuest:                acc.IsGuest,

backend/internal/server/handlers_admin_console.go

@@ -29,10 +29,6 @@ import (
 // adminPageSize is the page size of the admin console's paginated lists.
 const adminPageSize = 50
 
-// maxHintGrant caps a single operator hint grant. Grants are additive and can never lower a
-// wallet, so a fat-fingered grant cannot be undone through this form; the cap bounds one mistake.
-const maxHintGrant = 100
-
 // registerConsole mounts the server-rendered admin console under /_gm. The gateway
 // puts HTTP Basic-Auth in front of /_gm and reverse-proxies it verbatim; the
 // backend trusts the gateway (as for all of /api) and adds only a same-origin guard
@@ -56,7 +52,6 @@ func (s *Server) registerConsole(router *gin.Engine) {
 	gm.GET("/users/:id", s.consoleUserDetail)
 	gm.POST("/users/:id/message", s.consoleUserMessage)
 	gm.POST("/users/:id/clear-high-rate-flag", s.consoleClearHighRateFlag)
-	gm.POST("/users/:id/grant-hints", s.consoleGrantHints)
 	gm.POST("/users/:id/block", s.consoleBlockUser)
 	gm.POST("/users/:id/unblock", s.consoleUnblockUser)
 	gm.POST("/users/:id/grant-role", s.consoleGrantRole)
@@ -354,7 +349,6 @@ func (s *Server) consoleUserDetail(c *gin.Context) {
 	view := adminconsole.UserDetailView{
 		ID: acc.ID.String(), DisplayName: acc.DisplayName, Language: acc.PreferredLanguage,
 		TimeZone: acc.TimeZone, Guest: acc.IsGuest, NotificationsInAppOnly: acc.NotificationsInAppOnly,
-		PaidAccount: acc.PaidAccount, HintBalance: acc.HintBalance, HintGrantMax: maxHintGrant,
 		CreatedAt: fmtTime(acc.CreatedAt), HasStats: !acc.IsGuest, ConnectorEnabled: s.connector != nil,
 	}
 	if acc.MergedInto != uuid.Nil {
@@ -963,30 +957,6 @@ func (s *Server) consoleClearHighRateFlag(c *gin.Context) {
 	s.renderConsoleMessage(c, "Cleared", "high-rate flag cleared", "/_gm/users/"+id.String())
 }
 
-// consoleGrantHints adds hints to a user's wallet. The grant is additive (raise-only): it tops a
-// player up and can never lower what they already hold, so blocking a reduction is inherent rather
-// than a separate guard. A single grant is bounded by maxHintGrant.
-func (s *Server) consoleGrantHints(c *gin.Context) {
-	id, ok := s.consoleUUID(c, "/_gm/users")
-	if !ok {
-		return
-	}
-	back := "/_gm/users/" + id.String()
-	n, err := strconv.Atoi(trimForm(c, "amount"))
-	if err != nil || n < 1 || n > maxHintGrant {
-		s.renderConsoleMessage(c, "Invalid amount", fmt.Sprintf("enter a whole number of hints to add, between 1 and %d", maxHintGrant), back)
-		return
-	}
-	balance, err := s.accounts.GrantHints(c.Request.Context(), id, n)
-	if err != nil {
-		s.consoleError(c, err)
-		return
-	}
-	// A non-empty hint wallet removes the banner: nudge an open client to re-check.
-	s.publishBannerChange(id)
-	s.renderConsoleMessage(c, "Granted", fmt.Sprintf("added %d hint(s); the wallet is now %d", n, balance), back)
-}
-
 // consoleRemoveEmail deletes the account's bound email identity (and any pending
 // confirmations), freeing the address. It refuses to remove the account's only
 // identity, which would leave it unreachable.