feat: erweiterte Chat-Funktionalität, UI-Verbesserungen und Lokalisierungsupdates

- Chat: Nachrichten-Status (read/unread), WebSocket-Verbesserungen
- App: Login-Optimierung, Job-Übersicht verbessert, neue Übersetzungen
- Backend: Dialog-Styling, Invoice-Generator, Job-Verwaltung erweitert
- Mehrsprachigkeit: Neue Übersetzungen für DE, EN, ES, ET, FR, LT, LV, PL, RU, TR

app/lib/services/websocket_service.dart

@@ -13,6 +13,7 @@ import 'location_service.dart';
 import '../app_state.dart';
 import '../models/chat_message.dart';
 import '../models/job.dart';
+import '../models/queued_message.dart';
 import 'dart_mq.dart';
 
 class WebSocketService {
@@ -193,6 +194,73 @@ class WebSocketService {
     _reconnectTimer = null;
   }
 
+  /// Force a clean reconnect after the app resumes from standby.
+  /// Keeps buffered outbound messages intact and relies on saved credentials
+  /// for the subsequent auto-login inside [connect].
+  Future<void> reconnectForAppResume() async {
+    final credentials = await _databaseService.loadCredentials();
+    if (credentials == null) {
+      developer.log(
+        'Skipping reconnect after resume - no saved credentials',
+        name: 'WebSocketService',
+      );
+      return;
+    }
+
+    if (_isConnecting) {
+      developer.log(
+        'Skipping reconnect after resume - connection attempt already running',
+        name: 'WebSocketService',
+      );
+      return;
+    }
+
+    developer.log(
+      'Restarting WebSocket connection after app resume',
+      name: 'WebSocketService',
+    );
+
+    _stopReconnectTimer();
+
+    final existingSubscription = _wsSubscription;
+    final existingChannel = _wsChannel;
+
+    _wsSubscription = null;
+    _wsChannel = null;
+    _disconnectCompleter = null;
+    _isConnected = false;
+    _isConnecting = false;
+    _isAuthenticated = false;
+    _authToken = null;
+    _lastAuthResponse = null;
+
+    Future.microtask(() {
+      DartMQ().publish<bool>(MQTopics.connectionStatus, false);
+    });
+
+    try {
+      await existingSubscription?.cancel();
+    } catch (e, st) {
+      developer.log(
+        'Error cancelling old WebSocket subscription on resume: $e',
+        name: 'WebSocketService',
+      );
+      developer.log('Stack: $st', name: 'WebSocketService');
+    }
+
+    try {
+      await existingChannel?.sink.close(ws_status.goingAway);
+    } catch (e, st) {
+      developer.log(
+        'Error closing old WebSocket channel on resume: $e',
+        name: 'WebSocketService',
+      );
+      developer.log('Stack: $st', name: 'WebSocketService');
+    }
+
+    await connect();
+  }
+
   // ---------------------------------------------------------------------------
   // WebSocket Send / Receive
   // ---------------------------------------------------------------------------
@@ -290,6 +358,8 @@ class WebSocketService {
       _handleJobDeletedMessage(data);
     } else if (topic.endsWith('/job_created')) {
       _handleJobCreatedMessage(data);
+    } else if (topic.endsWith('/message_ack')) {
+      await _handleChatMessageAck(data);
     } else if (topic.endsWith('/message')) {
       await _handleChatMessage(topic, data);
     } else {
@@ -598,6 +668,20 @@ class WebSocketService {
     }
   }
 
+  Future<void> _handleChatMessageAck(Map<String, dynamic> data) async {
+    final clientMessageId = data['clientMessageId']?.toString().trim() ?? '';
+    if (clientMessageId.isEmpty) {
+      developer.log(
+        'Received message ACK without clientMessageId',
+        name: 'WebSocketService',
+      );
+      return;
+    }
+
+    await _databaseService.removeQueuedMessage(clientMessageId);
+    await ChatService().markOutgoingMessageSynced(clientMessageId);
+  }
+
   void _handleOtherClientMessage(String topic, Map<String, dynamic> data) {
     final type = data['type'];
     if (topic.contains('/tasks/') || type == 'task') {
@@ -731,6 +815,7 @@ class WebSocketService {
   /// Clears all local jobs and related data, then notifies the server.
   Future<void> _flushMessageBuffer() async {
     final initialBufferSize = _messageBuffer.length;
+    final sentQueuedChatCount = await _flushQueuedChatMessages();
 
     if (initialBufferSize > 0) {
       developer.log(
@@ -766,7 +851,8 @@ class WebSocketService {
     await _databaseService.clearAllJobsAndRelatedData();
 
     // Notify server that buffer flush is complete
-    final sentCount = initialBufferSize - _messageBuffer.length;
+    final sentCount =
+        (initialBufferSize - _messageBuffer.length) + sentQueuedChatCount;
     final bufferFlushedPayload = jsonEncode({
       'timestamp': DateTime.now().toIso8601String(),
       'messageCount': sentCount,
@@ -774,9 +860,51 @@ class WebSocketService {
     _sendWebSocket('/server/buffer_flushed', bufferFlushedPayload);
   }
 
+  Future<int> _flushQueuedChatMessages() async {
+    final queuedMessages = await _databaseService.getQueuedMessages();
+    if (queuedMessages.isEmpty) {
+      return 0;
+    }
+
+    developer.log(
+      'Flushing ${queuedMessages.length} queued chat messages',
+      name: 'WebSocketService',
+    );
+
+    var sentCount = 0;
+    for (final message in queuedMessages) {
+      final success = await _trySendQueuedChatMessage(
+        message,
+        incrementRetryOnFailure: true,
+      );
+      if (success) {
+        sentCount++;
+      }
+    }
+
+    return sentCount;
+  }
+
+  Future<bool> _trySendQueuedChatMessage(
+    QueuedMessage message, {
+    bool incrementRetryOnFailure = false,
+  }) async {
+    if (!_isConnected || !_isAuthenticated || _wsChannel == null) {
+      return false;
+    }
+
+    final success = _sendWebSocket(message.topic, jsonEncode(message.payload));
+    if (!success && incrementRetryOnFailure) {
+      await _databaseService.updateMessageRetryCount(
+        message.id,
+        message.retryCount + 1,
+      );
+    }
+    return success;
+  }
+
   /// Publish a chat message according to the backend contract.
-  /// Returns the locally constructed message so callers can persist it locally.
-  /// Messages are buffered if offline and sent automatically when reconnected.
+  /// The message is stored locally and remains queued until the server confirms it.
   Future<ChatMessage?> sendChatMessage({
     required String sender,
     required String receiver,
@@ -790,6 +918,9 @@ class WebSocketService {
     final trimmedContent = content.trim();
     final normalizedJobId = jobId?.trim();
     final normalizedJobNumber = jobNumber?.trim();
+    final hasJobContext =
+        (normalizedJobId?.isNotEmpty ?? false) ||
+        (normalizedJobNumber?.isNotEmpty ?? false);
 
     if (trimmedSender.isEmpty ||
         trimmedReceiver.isEmpty ||
@@ -816,6 +947,9 @@ class WebSocketService {
       'receiver': trimmedReceiver,
       'content': trimmedContent,
     };
+    final now = DateTime.now();
+    final clientMessageId = 'local-${now.microsecondsSinceEpoch}';
+    payload['messageId'] = clientMessageId;
 
     if (normalizedJobId != null && normalizedJobId.isNotEmpty) {
       payload['jobId'] = normalizedJobId;
@@ -828,18 +962,13 @@ class WebSocketService {
     const topic = '/server/message';
 
     try {
-      final jsonPayload = jsonEncode(payload);
-      // sendMessage buffers automatically if not connected/authenticated
-      sendMessage(topic, jsonPayload);
-
-      final now = DateTime.now();
       final message = ChatMessage(
-        id: 'local-${now.microsecondsSinceEpoch}',
+        id: clientMessageId,
         content: trimmedContent,
         createdAt: now,
         direction: ChatDirection.outgoing,
         messageType:
-            normalizedJobId != null && normalizedJobId.isNotEmpty
+            hasJobContext
                 ? ChatMessageType.jobRelated
                 : ChatMessageType.general,
         contentType: contentType,
@@ -849,13 +978,26 @@ class WebSocketService {
         read: false,
         pendingSync: true,
       );
+      final queuedMessage = QueuedMessage(
+        id: clientMessageId,
+        topic: topic,
+        payload: payload,
+        createdAt: now,
+      );
+
+      await _databaseService.queueMessage(queuedMessage);
+      await ChatService().saveOutgoingMessage(message);
+      final sentImmediately = await _trySendQueuedChatMessage(queuedMessage);
+      if (!sentImmediately) {
+        developer.log(
+          'Chat message $clientMessageId queued for retry after reconnect',
+          name: 'WebSocketService',
+        );
+      }
 
       return message;
     } catch (e, st) {
-      developer.log(
-        'Error encoding chat message payload: $e',
-        name: 'WebSocketService',
-      );
+      developer.log('Error sending chat message: $e', name: 'WebSocketService');
       developer.log('Stack: $st', name: 'WebSocketService');
       return null;
     }