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

test/account_config_test.dart

@@ -0,0 +1,67 @@
+// SPDX-FileCopyrightText: 2026 TatuChat
+//
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:tatchat/utils/account_config.dart';
+
+void main() {
+  group('ApplicationAccountConfig', () {
+    test('Parses primary color from account data', () {
+      final config = ApplicationAccountConfig.fromJson({
+        'primary_color': 0xFF6750A4,
+      });
+      expect(config.primaryColor, 0xFF6750A4);
+    });
+
+    test('Ignores primary color of unexpected type', () {
+      expect(
+        ApplicationAccountConfig.fromJson({
+          'primary_color': '4286369748',
+        }).primaryColor,
+        isNull,
+      );
+      expect(
+        ApplicationAccountConfig.fromJson({'primary_color': 1.5}).primaryColor,
+        isNull,
+      );
+    });
+
+    test('Defaults primary color to null when absent', () {
+      expect(ApplicationAccountConfig.fromJson({}).primaryColor, isNull);
+    });
+
+    test('Serializes primary color', () {
+      const config = ApplicationAccountConfig(primaryColor: 0xFF00D084);
+      expect(config.toJson()['primary_color'], 0xFF00D084);
+    });
+
+    test('Serializes missing primary color as null', () {
+      const config = ApplicationAccountConfig(wallpaperOpacity: 0.5);
+      expect(config.toJson()['primary_color'], isNull);
+    });
+
+    test('Round trips through json', () {
+      final config = ApplicationAccountConfig(
+        wallpaperUrl: Uri.parse('mxc://example.invalid/wallpaper'),
+        wallpaperOpacity: 0.3,
+        wallpaperBlur: 4,
+        primaryColor: 0xFF6750A4,
+      );
+      final parsed = ApplicationAccountConfig.fromJson(config.toJson());
+      expect(parsed.wallpaperUrl, config.wallpaperUrl);
+      expect(parsed.wallpaperOpacity, config.wallpaperOpacity);
+      expect(parsed.wallpaperBlur, config.wallpaperBlur);
+      expect(parsed.primaryColor, config.primaryColor);
+    });
+
+    test('Keeps existing wallpaper defaults when parsing color only', () {
+      final config = ApplicationAccountConfig.fromJson({
+        'primary_color': 0xFF6750A4,
+      });
+      expect(config.wallpaperUrl, isNull);
+      expect(config.wallpaperOpacity, 1);
+      expect(config.wallpaperBlur, isNull);
+    });
+  });
+}