feat(ads): server-driven ad-banner backend, wire & admin console (PR1)

Turn the gated-off mock banner into a real advertising subsystem (backend +
admin half; the UI rotation lands in PR2).

- internal/ads: campaigns (percent weight + validity window; a perpetual,
  undeletable default that fills the remainder up to 100%), 1..N bilingual
  messages (en+ru), global display timings; ActiveSet computes the
  window-filtered, default-remainder, GCD-reduced, language-resolved rotation
  feed. Smooth-weighted-round-robin math is unit-tested.
- migration 00006 (+ jetgen): ad_campaigns / ad_messages / ad_settings, seeded
  default campaign + house message + default timings.
- eligibility = !paid_account && hint_balance==0 && !no_banner role (new role;
  guests qualify). The resolved feed rides the profile.get response (no new RPC,
  works for guests, nothing distinct to filter); language by service_language.
- live update: a notify `banner` sub-kind (re-poll signal) published when an
  operator grants hints or grants/revokes no_banner, so the client shows/hides
  in place.
- admin console /_gm/banners (+ /_gm/banner-settings): campaign + message CRUD
  with reorder, default protection, clamped timings.
- wire: fbs BannerInfo/BannerCampaign on Profile; gateway transcode forwards it.
- docs: ARCHITECTURE §10, FUNCTIONAL (+ _ru), backend README, PRERELEASE tracker
  (incl. the deferred app.load aggregator note).

backend/internal/server/server.go

@@ -19,12 +19,14 @@ import (
 
 	"scrabble/backend/internal/account"
 	"scrabble/backend/internal/adminconsole"
+	"scrabble/backend/internal/ads"
 	"scrabble/backend/internal/connector"
 	"scrabble/backend/internal/engine"
 	"scrabble/backend/internal/feedback"
 	"scrabble/backend/internal/game"
 	"scrabble/backend/internal/link"
 	"scrabble/backend/internal/lobby"
+	"scrabble/backend/internal/notify"
 	"scrabble/backend/internal/ratewatch"
 	"scrabble/backend/internal/session"
 	"scrabble/backend/internal/social"
@@ -81,6 +83,14 @@ type Deps struct {
 	// admin console's throttled view + the high-rate auto-flag. A nil RateWatch
 	// disables the internal report endpoint and the console view.
 	RateWatch *ratewatch.Watch
+	// Ads is the advertising-banner domain service: campaign rotation feeding the
+	// profile.get banner block, plus the banner admin console section. A nil Ads
+	// omits the banner block and disables the banner console.
+	Ads *ads.Service
+	// Notifier publishes live-event intents — here the banner-eligibility re-poll
+	// signal the banner/hint/role console actions emit. A nil Notifier discards
+	// them (notify.Nop).
+	Notifier notify.Publisher
 }
 
 // Server owns the gin engine, the underlying HTTP server and the readiness
@@ -105,6 +115,8 @@ type Server struct {
 	dictDir     string
 	connector   *connector.Client
 	ratewatch   *ratewatch.Watch
+	ads         *ads.Service
+	notifier    notify.Publisher
 	console     *adminconsole.Renderer
 
 	public   *gin.RouterGroup
@@ -129,6 +141,11 @@ func New(addr string, deps Deps) *Server {
 	engine.Use(gin.Recovery())
 	engine.Use(telemetry.Middleware(log))
 
+	notifier := deps.Notifier
+	if notifier == nil {
+		notifier = notify.Nop{}
+	}
+
 	s := &Server{
 		log:           log,
 		db:            deps.DB,
@@ -147,6 +164,8 @@ func New(addr string, deps Deps) *Server {
 		dictDir:       deps.DictDir,
 		connector:     deps.Connector,
 		ratewatch:     deps.RateWatch,
+		ads:           deps.Ads,
+		notifier:      notifier,
 		http:          &http.Server{Addr: addr, Handler: engine},
 	}
 	s.registerProbes(engine)