feat(chats): очистка истории и удаление чата из меню

lib/backend/modules/chats.dart

@@ -7,6 +7,7 @@ import '../../core/config/komet_settings.dart';
 import '../../core/protocol/opcode_map.dart';
 import '../../core/protocol/packet.dart';
 import '../../core/cache/info_cache.dart';
+import '../../core/cache/message_session_cache.dart';
 import '../../core/storage/app_database.dart';
 import '../../core/storage/token_storage.dart';
 import '../../core/utils/logger.dart';
@@ -1520,6 +1521,35 @@ class ChatsModule {
     }
   }
 
+  static Future<String?> clearHistory(
+    Api api, {
+    required int chatId,
+    required int lastEventTime,
+    bool forAll = false,
+  }) async {
+    try {
+      await api.sendRequest(Opcode.chatClear, {
+        'chatId': chatId,
+        'lastEventTime': lastEventTime,
+        'forAll': forAll,
+      });
+      final accountId = await TokenStorage.getActiveAccountId();
+      if (accountId != null) {
+        await AppDatabase.clearMessages(accountId, chatId);
+        MessageSessionCache.remove(accountId, chatId);
+        _historyFetched.remove(chatId);
+        await reconcileLastMessage(accountId, chatId);
+      }
+      return null;
+    } on PacketError catch (e) {
+      logger.w('clearHistory $chatId: ${e.message}');
+      return e.message;
+    } catch (e) {
+      logger.w('clearHistory $chatId: $e');
+      return 'Не удалось очистить историю';
+    }
+  }
+
   static Future<bool> leaveChat(Api api, {required int chatId}) async {
     try {
       await api.sendRequest(Opcode.chatLeave, {'chatId': chatId});

lib/frontend/screens/chats/chat_screen.dart

@@ -2349,17 +2349,93 @@ class _ChatScreenState extends State<ChatScreen>
         ChatMenuItem(
           icon: Symbols.mop,
           label: 'Очистить историю',
-          onTap: () {},
+          onTap: _clearHistory,
         ),
         ChatMenuItem(
           icon: Symbols.delete,
           label: 'Удалить чат',
-          onTap: () {},
+          onTap: _deleteChat,
         ),
       ],
     );
   }
 
+  Future<bool?> _showConfirmDialog({
+    required String title,
+    required String body,
+    required String confirmLabel,
+  }) {
+    final cs = Theme.of(context).colorScheme;
+    return showDialog<bool>(
+      context: context,
+      builder: (ctx) => AlertDialog(
+        backgroundColor: cs.surfaceContainerHigh,
+        title: Text(title),
+        content: Text(
+          body,
+          style: TextStyle(color: cs.onSurfaceVariant, fontSize: 15),
+        ),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(ctx, false),
+            child: const Text('Отмена'),
+          ),
+          TextButton(
+            onPressed: () => Navigator.pop(ctx, true),
+            child: Text(confirmLabel, style: TextStyle(color: cs.error)),
+          ),
+        ],
+      ),
+    );
+  }
+
+  Future<void> _clearHistory() async {
+    final confirmed = await _showConfirmDialog(
+      title: 'Очистить историю',
+      body: 'Все сообщения в этом чате будут удалены без возможности '
+          'восстановления.',
+      confirmLabel: 'Очистить',
+    );
+    if (!mounted || confirmed != true) return;
+    final err = await ChatsModule.clearHistory(
+      api,
+      chatId: widget.chatId,
+      lastEventTime: chat?.lastEventTime ?? 0,
+    );
+    if (!mounted) return;
+    if (err != null) {
+      showCustomNotification(context, err);
+      return;
+    }
+    setState(() {
+      _messages = [];
+      _hasMoreHistory = false;
+      _combinedItemsCache = null;
+    });
+    _messagesRev.value++;
+  }
+
+  Future<void> _deleteChat() async {
+    final confirmed = await _showConfirmDialog(
+      title: 'Удалить чат',
+      body: 'Чат будет удалён вместе со всей перепиской.',
+      confirmLabel: 'Удалить',
+    );
+    if (!mounted || confirmed != true) return;
+    final err = await ChatsModule.deleteChat(
+      api,
+      chatId: widget.chatId,
+      lastEventTime: chat?.lastEventTime ?? 0,
+      forAll: false,
+    );
+    if (!mounted) return;
+    if (err != null) {
+      showCustomNotification(context, err);
+      return;
+    }
+    Navigator.of(context).pop();
+  }
+
   Future<void> _startCall() async {
     if (widget.chatType != 'DIALOG') {
       showCustomNotification(context, 'Звонки доступны только в диалогах');