feat(auth): server-side sessions and current password for account changes (FLAW-30, FLAW-31)

- Every login is a session (device, IP, last use); the token's jti is its ID.
  Sessions end on logout, per device from the profile, or after 30 idle days.
- Tokens older than a day are renewed via the X-Session-Token header.
- Changing password or login e-mail needs the current password; a new
  password logs out all other devices and mails the old address.
- Demo reset keeps the demo visitors' sessions.
- revoked_tokens is replaced by sessions (migration 4); everyone is logged
  out once after the upgrade.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/server.go

@@ -97,7 +97,7 @@ func (s *Server) Router() http.Handler {
 		AllowedOrigins:   allowedOrigins,
 		AllowedMethods:   []string{"GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"},
 		AllowedHeaders:   []string{"Accept", "Authorization", "Content-Type", "X-API-Key"},
-		ExposedHeaders:   []string{"Link"},
+		ExposedHeaders:   []string{"Link", "X-Session-Token"},
 		AllowCredentials: false,
 		MaxAge:           300,
 	}))
@@ -125,6 +125,8 @@ func (s *Server) Router() http.Handler {
 		r.Get("/api/v1/auth/me", s.handleMe)
 		r.Post("/api/v1/events/rooms", s.handleSSERooms)
 		r.Post("/api/v1/auth/stream-ticket", s.handleStreamTicket)
+		r.Get("/api/v1/auth/sessions", s.handleListSessions)
+		r.Delete("/api/v1/auth/sessions/{id}", s.handleEndSession)
 		r.Post("/api/v1/auth/logout", s.handleLogout)
 		r.Post("/api/v1/auth/revoke-all", s.handleRevokeAllSessions)
 		r.Patch("/api/v1/auth/settings", s.handleUpdateUserSettings)
@@ -417,7 +419,7 @@ func (s *Server) authenticateToken(token string) (user *domain.User, keyScopes [
 		return u, scopes
 	}
 	claims, err := auth.ValidateToken(s.cfg.JWTSecret, token)
-	if err != nil || claims == nil || s.store.IsTokenRevoked(token) {
+	if err != nil || claims == nil {
 		return nil, nil
 	}
 	u, err := s.store.GetUserByID(claims.UserID)
@@ -427,6 +429,10 @@ func (s *Server) authenticateToken(token string) (user *domain.User, keyScopes [
 	if claims.TokenVersion != 0 && claims.TokenVersion != u.TokenVersion {
 		return nil, nil
 	}
+	// Logged out, ended from the session list or idle for 30 days
+	if !s.store.SessionActive(claims.ID, u.ID) {
+		return nil, nil
+	}
 	return u, nil
 }
 
@@ -478,6 +484,12 @@ func (s *Server) authMiddleware(next http.Handler) http.Handler {
 			return
 		}
 		ctx := auth.WithUserID(r.Context(), user.ID)
+		if keyScopes == nil {
+			if claims, err := auth.ValidateToken(s.cfg.JWTSecret, token); err == nil {
+				ctx = withSession(ctx, claims.ID)
+				s.renewSessionToken(w, user, claims, false)
+			}
+		}
 		if keyScopes != nil {
 			if !apiKeyAllowed(r) {
 				writeError(w, http.StatusForbidden, "API-Keys dürfen nur Daten einliefern (POST /api/v1/inbox oder /api/v1/webhooks/ingest)")