feat: sincronizar cor do tema via account data da conta Matrix

A cor escolhida no Appearance passa a ser guardada em im.fluffychat.account_config (primary_color), em vez de apenas nas preferencias locais do dispositivo.

- ApplicationAccountConfig ganha primaryColor, preservado em updateApplicationAccountConfig e no novo setApplicationAccountColor
- ThemeController restaura a cor da conta activa, aguarda accountDataLoading e reage a alteracoes remotas via onSync
- A cor final e derivada de _accountPrimaryColor ?? _localPrimaryColor, evitando corrida entre as preferencias locais e o sync
- Matrix notifica a troca de conta activa em initMatrix, setActiveClient e logout, corrigindo o indice do cliente activo
- Apagar o wallpaper preserva a cor; testes de serializacao do modelo

lib/widgets/matrix.dart

@@ -44,10 +44,13 @@ class Matrix extends StatefulWidget {
 
   final SharedPreferences store;
 
+  final ValueChanged<Client?>? onActiveClientChanged;
+
   const Matrix({
     this.child,
     required this.clients,
     required this.store,
+    this.onActiveClientChanged,
     this.queryParameters,
     super.key,
   });
@@ -89,11 +92,21 @@ class MatrixState extends State<Matrix> {
     final i = widget.clients.indexWhere((c) => c == cl);
     if (i != -1) {
       _activeClient = i;
+      _notifyActiveClientChanged();
     } else {
       Logs().w('Tried to set an unknown client ${cl!.userID} as active');
     }
   }
 
+  void _notifyActiveClientChanged() {
+    final callback = widget.onActiveClientChanged;
+    if (callback == null) return;
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (!mounted) return;
+      callback(widget.clients.isEmpty ? null : client);
+    });
+  }
+
   List<Client?>? get currentBundle {
     if (!hasComplexBundles) {
       return List.from(widget.clients);
@@ -256,19 +269,27 @@ class MatrixState extends State<Matrix> {
         .where((state) => state == LoginState.loggedOut)
         .listen((_) {
           final loggedInWithMultipleClients = widget.clients.length > 1;
+          final activeClient = client;
+          final removedIndex = widget.clients.indexOf(c);
+          final wasActive = removedIndex != -1 && activeClient == c;
 
           _cancelSubs(c.clientName);
           widget.clients.remove(c);
           ClientManager.removeClientNameFromStore(c.clientName, store);
           InitWithRestoreExtension.deleteSessionBackup(name);
+          if (removedIndex != -1 && _activeClient > removedIndex) {
+            _activeClient--;
+          }
+          if (wasActive) {
+            _activeClient = -1;
+          }
+          if (removedIndex != -1) {
+            _notifyActiveClientChanged();
+          }
 
           if (loggedInWithMultipleClients) {
             final snackbarContext =
-                TatuChatApp
-                    .router
-                    .routerDelegate
-                    .navigatorKey
-                    .currentContext ??
+                TatuChatApp.router.routerDelegate.navigatorKey.currentContext ??
                 context;
 
             if (!snackbarContext.mounted) return;
@@ -349,6 +370,7 @@ class MatrixState extends State<Matrix> {
         },
       );
     }
+    _notifyActiveClientChanged();
   }
 
   void didChangeAppLifecycleState(AppLifecycleState state) {