feat: 实现 sessions 持久化，支持会话恢复

backend/cmd/server/main.go

@@ -53,6 +53,7 @@ func main() {
 
 	var userRepo store.UserRepository
 	var msgRepo store.MessageRepository
+	var sessRepo store.SessionRepository
 
 	if cfg.Storage.Driver == "postgres" {
 		pool, err := store.NewPostgresPool(ctx, cfg.Storage.DSN)
@@ -68,6 +69,7 @@ func main() {
 
 		userRepo = store.NewPgUserRepository(pool)
 		msgRepo = store.NewPgMessageRepository(pool)
+		sessRepo = store.NewPgSessionRepository(pool)
 		logger.Log.Infow("postgres storage initialized", "driver", cfg.Storage.Driver)
 	} else {
 		userRepo = store.NewMemUserRepository()
@@ -80,6 +82,9 @@ func main() {
 	if msgRepo != nil {
 		sessionOpts = append(sessionOpts, session.WithMessageRepository(msgRepo))
 	}
+	if sessRepo != nil {
+		sessionOpts = append(sessionOpts, session.WithSessionRepository(sessRepo))
+	}
 	sessionMgr = session.NewMemoryManager(
 		time.Duration(cfg.Session.TTL)*time.Minute,
 		cfg.Session.MaxHistory,