Add code resolver, sync conflict handling, and user isolation

Introduce a CodeResolverService to classify user login codes, complete with detailed resolution logic and usability checks. Extend the sync system to handle conflicts via last-write-wins arbitration, with detailed conflict tracking for review. Update file permissions and runtime isolation in Docker to enhance security.

client/app/lib/api.dart

@@ -370,20 +370,49 @@ class FileEntry {
 }
 
 class ChatChannel {
-  ChatChannel({required this.id, required this.type});
+  ChatChannel({
+    required this.id,
+    required this.type,
+    this.name,
+    this.gemeindeId,
+    this.createdByUserId,
+  });
   final String id;
   final String type;
+  final String? name;
+  final String? gemeindeId;
+  final String? createdByUserId;
+
   factory ChatChannel.fromJson(Map<String, dynamic> j) => ChatChannel(
         id: j['id'] as String,
         type: j['type'] as String? ?? '',
+        name: j['name'] as String?,
+        gemeindeId: j['gemeindeId'] as String?,
+        createdByUserId: j['createdByUserId'] as String?,
       );
 }
 
 class ChatMessage {
-  ChatMessage({required this.body, required this.createdAt});
+  ChatMessage({
+    this.id,
+    this.channelId,
+    this.senderUserId,
+    this.senderGuestId,
+    required this.body,
+    required this.createdAt,
+  });
+  final String? id;
+  final String? channelId;
+  final String? senderUserId;
+  final String? senderGuestId;
   final String body;
   final String createdAt;
+
   factory ChatMessage.fromJson(Map<String, dynamic> j) => ChatMessage(
+        id: j['id'] as String?,
+        channelId: j['channelId'] as String?,
+        senderUserId: j['senderUserId'] as String?,
+        senderGuestId: j['senderGuestId'] as String?,
         body: j['body'] as String? ?? '',
         createdAt: j['createdAt'] as String? ?? '',
       );