Stage 4: lobby & social (matchmaking, friends, blocks, chat+nudge, invitations, profile, email, multi-player drop-out)

Engine: multi-player drop-out-and-continue with a per-game tile disposition (remove default / return), resigned seats skipped and excluded from the win, leaver rack never revealed; 2-player behaviour unchanged.

New domains (service/store, no HTTP yet): internal/social (friend request/accept graph, per-user blocks, per-game chat with nudge as a message kind, content filter via mvdan.cc/xurls/v2 + leet/separator normaliser + phone heuristic) and internal/lobby (in-memory variant-keyed matchmaking pool, friend-game invitations invite->accept with lazy 7-day expiry). account gains profile editing and the email confirm-code flow (Mailer seam: SMTP or log mailer).

Migration 00003_social.sql + regenerated jet. main wires the new services into the server (accessors for the Stage 6 handlers); robot substitution stays in Stage 5, REST/stream/push in Stage 6/8. Docs (PLAN, ARCHITECTURE, FUNCTIONAL+ru, TESTING, README) updated.

backend/internal/server/server.go

@@ -17,6 +17,9 @@ import (
 	"github.com/gin-gonic/gin"
 	"go.uber.org/zap"
 
+	"scrabble/backend/internal/account"
+	"scrabble/backend/internal/lobby"
+	"scrabble/backend/internal/social"
 	"scrabble/backend/internal/telemetry"
 )
 
@@ -39,6 +42,14 @@ type Deps struct {
 	// SessionsReady reports whether the session cache has been warmed. A nil
 	// func skips the session-readiness check.
 	SessionsReady func() bool
+	// Social, Matchmaker, Invitations and Emails are the Stage 4 domain services.
+	// They are held for the REST/stream handlers the gateway adds in Stage 6 (like
+	// the route groups, this is scaffolding exposed via accessors); the server
+	// itself does not route to them yet.
+	Social      *social.Service
+	Matchmaker  *lobby.Matchmaker
+	Invitations *lobby.InvitationService
+	Emails      *account.EmailService
 }
 
 // Server owns the gin engine, the underlying HTTP server and the readiness
@@ -50,6 +61,11 @@ type Server struct {
 	pingTimeout   time.Duration
 	sessionsReady func() bool
 
+	social      *social.Service
+	matchmaker  *lobby.Matchmaker
+	invitations *lobby.InvitationService
+	emails      *account.EmailService
+
 	public   *gin.RouterGroup
 	user     *gin.RouterGroup
 	internal *gin.RouterGroup
@@ -78,6 +94,10 @@ func New(addr string, deps Deps) *Server {
 		db:            deps.DB,
 		pingTimeout:   pingTimeout,
 		sessionsReady: deps.SessionsReady,
+		social:        deps.Social,
+		matchmaker:    deps.Matchmaker,
+		invitations:   deps.Invitations,
+		emails:        deps.Emails,
 		http:          &http.Server{Addr: addr, Handler: engine},
 	}
 	s.registerProbes(engine)
@@ -136,6 +156,18 @@ func (s *Server) InternalGroup() *gin.RouterGroup { return s.internal }
 // AdminGroup returns the admin route group (authenticated at the gateway).
 func (s *Server) AdminGroup() *gin.RouterGroup { return s.admin }
 
+// Social returns the social domain service for the handlers added in Stage 6.
+func (s *Server) Social() *social.Service { return s.social }
+
+// Matchmaker returns the in-memory matchmaking pool for the Stage 6 handlers.
+func (s *Server) Matchmaker() *lobby.Matchmaker { return s.matchmaker }
+
+// Invitations returns the friend-game invitation service for the Stage 6 handlers.
+func (s *Server) Invitations() *lobby.InvitationService { return s.invitations }
+
+// Emails returns the email confirm-code service for the Stage 6 handlers.
+func (s *Server) Emails() *account.EmailService { return s.emails }
+
 // Handler returns the underlying HTTP handler. It lets tests drive the server
 // without binding a socket and lets later stages compose the backend behind
 // another listener.