feat: runtime config, Matomo analytics, chat accounts, DM history/search, and Prometheus retention

backend/chat/src/auth/auth.go

@@ -137,4 +137,52 @@ func RequireAdmin(store *SessionStore, cookieName string) func(http.HandlerFunc)
 			next(w, r)
 		}
 	}
+}
+
+// UserSessionStore maps user session tokens to usernames with expiry.
+type UserSessionStore struct {
+	mu       sync.Mutex
+	sessions map[string]userSession
+}
+
+type userSession struct {
+	Username  string
+	ExpiresAt time.Time
+}
+
+// NewUserSessionStore creates a new user session store.
+func NewUserSessionStore() *UserSessionStore {
+	return &UserSessionStore{sessions: make(map[string]userSession)}
+}
+
+// Add stores a user session token with username and expiry.
+func (s *UserSessionStore) Add(token, username string, expiresAt time.Time) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.sessions[token] = userSession{Username: username, ExpiresAt: expiresAt}
+}
+
+// Username returns the username for a valid, unexpired token.
+func (s *UserSessionStore) Username(token string) (string, bool) {
+	if token == "" {
+		return "", false
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	sess, ok := s.sessions[token]
+	if !ok {
+		return "", false
+	}
+	if time.Now().After(sess.ExpiresAt) {
+		delete(s.sessions, token)
+		return "", false
+	}
+	return sess.Username, true
+}
+
+// Remove deletes a user session token.
+func (s *UserSessionStore) Remove(token string) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	delete(s.sessions, token)
 }