feat: add message translation support

- Introduced translation functionality in chat screen, allowing users to translate messages before sending.
- Added MessageTranslationButton to the input bar for enabling/disabling translation.
- Implemented translation service to handle incoming and outgoing text translations using llama models.
- Enhanced message storage to include original and translated text, language codes, and translation status.
- Created UI components for displaying translated messages and managing translation options.
- Added translation model management, including downloading and storing models locally.
- Updated app settings to manage translation preferences and model selections.

lib/models/message.dart

@@ -1,19 +1,27 @@
 import 'dart:typed_data';
 import '../connector/meshcore_protocol.dart';
 import '../helpers/reaction_helper.dart';
+import 'translation_support.dart';
 
 enum MessageStatus { pending, sent, delivered, failed }
 
 class Message {
+  static const Object _unset = Object();
+
   final Uint8List senderKey;
   final String text;
   final DateTime timestamp;
   final bool isOutgoing;
   final bool isCli;
   final MessageStatus status;
+  final String? originalText;
+  final String? translatedText;
+  final String? translatedLanguageCode;
+  final MessageTranslationStatus translationStatus;
+  final String? translationModelId;
 
   // NEW: Retry logic fields
-  final String? messageId;
+  final String messageId;
   final int retryCount;
   final int? estimatedTimeoutMs;
   final int? expectedAckHash;
@@ -33,7 +41,12 @@ class Message {
     required this.isOutgoing,
     this.isCli = false,
     this.status = MessageStatus.pending,
-    this.messageId,
+    String? messageId,
+    this.originalText,
+    this.translatedText,
+    this.translatedLanguageCode,
+    this.translationStatus = MessageTranslationStatus.none,
+    this.translationModelId,
     this.retryCount = 0,
     this.estimatedTimeoutMs,
     this.expectedAckHash,
@@ -45,7 +58,10 @@ class Message {
     Uint8List? fourByteRoomContactKey,
     Map<String, int>? reactions,
     Map<String, MessageStatus>? reactionStatuses,
-  }) : pathBytes = pathBytes ?? Uint8List(0),
+  }) : messageId =
+           messageId ??
+           '${timestamp.millisecondsSinceEpoch}_${pubKeyToHex(senderKey)}_${text.hashCode}',
+       pathBytes = pathBytes ?? Uint8List(0),
        fourByteRoomContactKey = fourByteRoomContactKey ?? Uint8List(0),
        reactions = reactions ?? {},
        reactionStatuses = reactionStatuses ?? {};
@@ -63,6 +79,11 @@ class Message {
     int? pathLength,
     Uint8List? pathBytes,
     bool? isCli,
+    Object? originalText = _unset,
+    Object? translatedText = _unset,
+    Object? translatedLanguageCode = _unset,
+    MessageTranslationStatus? translationStatus,
+    Object? translationModelId = _unset,
     Map<String, int>? reactions,
     Map<String, MessageStatus>? reactionStatuses,
     Uint8List? fourByteRoomContactKey,
@@ -75,6 +96,19 @@ class Message {
       isCli: isCli ?? this.isCli,
       status: status ?? this.status,
       messageId: messageId,
+      originalText: originalText == _unset
+          ? this.originalText
+          : originalText as String?,
+      translatedText: translatedText == _unset
+          ? this.translatedText
+          : translatedText as String?,
+      translatedLanguageCode: translatedLanguageCode == _unset
+          ? this.translatedLanguageCode
+          : translatedLanguageCode as String?,
+      translationStatus: translationStatus ?? this.translationStatus,
+      translationModelId: translationModelId == _unset
+          ? this.translationModelId
+          : translationModelId as String?,
       retryCount: retryCount ?? this.retryCount,
       estimatedTimeoutMs: estimatedTimeoutMs ?? this.estimatedTimeoutMs,
       expectedAckHash: expectedAckHash ?? this.expectedAckHash,
@@ -124,12 +158,18 @@ class Message {
   static Message outgoing(
     Uint8List recipientKey,
     String text, {
+    String? originalText,
+    String? translatedLanguageCode,
+    String? translationModelId,
     int? pathLength,
     Uint8List? pathBytes,
   }) {
     return Message(
       senderKey: recipientKey,
       text: text,
+      originalText: originalText,
+      translatedLanguageCode: translatedLanguageCode,
+      translationModelId: translationModelId,
       timestamp: DateTime.now(),
       isOutgoing: true,
       isCli: false,