fix: improve message sending logic and handle range download errors in translation service

lib/screens/channel_chat_screen.dart

@@ -1162,13 +1162,6 @@ class _ChannelChatScreenState extends State<ChannelChatScreen> {
     }
     _lastChannelSendAt = now;
 
-    // Capture reply state before clearing, then clear input synchronously
-    // to prevent double-send during async translation.
-    final replyingTo = _replyingToMessage;
-    _textController.clear();
-    _cancelReply();
-    _textFieldFocusNode.requestFocus();
-
     final connector = context.read<MeshCoreConnector>();
     final settings = context.read<AppSettingsService>().settings;
     final translationService = context.read<TranslationService>();
@@ -1200,8 +1193,8 @@ class _ChannelChatScreenState extends State<ChannelChatScreen> {
         }
       }
     }
-    if (replyingTo != null) {
+    if (_replyingToMessage != null) {
-      messageText = '@[${replyingTo.senderName}] $messageText';
+      messageText = '@[${_replyingToMessage!.senderName}] $messageText';
     }
 
     final maxBytes = maxChannelMessageBytes(connector.selfName);
@@ -1212,6 +1205,9 @@ class _ChannelChatScreenState extends State<ChannelChatScreen> {
       return;
     }
 
+    _textController.clear();
+    _cancelReply();
+    _textFieldFocusNode.requestFocus();
     connector.sendChannelMessage(
       widget.channel,
       messageText,

lib/screens/chat_screen.dart

@@ -642,10 +642,6 @@ class _ChatScreenState extends State<ChatScreen> {
     }
     _lastTextSendAt = now;
 
-    // Clear input synchronously to prevent double-send
-    _textController.clear();
-    _textFieldFocusNode.requestFocus();
-
     final settings = context.read<AppSettingsService>().settings;
     final translationService = context.read<TranslationService>();
     var outgoingText = text;
@@ -683,6 +679,8 @@ class _ChatScreenState extends State<ChatScreen> {
       return;
     }
 
+    _textController.clear();
+    _textFieldFocusNode.requestFocus();
     connector.sendMessage(
       _resolveContact(connector),
       outgoingText,

lib/services/translation_service.dart

@@ -317,8 +317,12 @@ class TranslationService extends ChangeNotifier {
     final request = http.Request('GET', uri);
     request.headers['Range'] = 'bytes=$start-$end';
     final response = await client.send(request);
-    if (response.statusCode != 206 && response.statusCode != 200) {
+    if (response.statusCode != 206) {
-      throw StateError('Range download failed: HTTP ${response.statusCode}');
+      await response.stream.drain<void>();
+      throw StateError(
+        'Range download failed: HTTP ${response.statusCode}'
+        '${response.statusCode == 200 ? ' (server ignored Range header)' : ''}',
+      );
     }
     final trackedStream = _trackDownloadProgress(response.stream);
     await _fileStore.writeModelBytes(