🔄 Changes

Core Features
Unread Message Tracking: Added persistent unread counts for contacts and channels with visual badges
Message Deletion: Users can now long-press to delete individual messages in chats and channels
SMAZ Compression: Added per-contact compression settings (previously only channels)
UTF-8 Length Limiting: Text inputs now enforce protocol byte limits correctly
Channel Message Paths: New screen to visualize packet routing through repeater network with map view
Protocol Updates
Added maxContactMessageBytes() and maxChannelMessageBytes() helpers for message length validation
Changed channel PSK format from Base64 to Hexadecimal (breaking change)
Added app version field to connection handshake frame
UI Improvements
Unread badges on all contact and channel list items
Enhanced message bubbles with path visualization for channel messages
Character count displays in message input fields
Improved repeater CLI screen functionality
New Files
lib/storage/unread_store.dart - Unread tracking persistence
lib/storage/contact_settings_store.dart - Per-contact SMAZ settings
lib/widgets/unread_badge.dart - Unread count indicator
lib/helpers/utf8_length_limiter.dart - Byte-aware text input formatter
lib/screens/channel_message_path_screen.dart - Packet path visualization

lib/connector/meshcore_protocol.dart

@@ -86,6 +86,35 @@ const int pathHashSize = 1;
 const int maxNameSize = 32;
 const int maxFrameSize = 172;
 const int appProtocolVersion = 3;
+// Matches firmware MAX_TEXT_LEN (10 * CIPHER_BLOCK_SIZE).
+const int maxTextPayloadBytes = 160;
+const int _sendTextMsgOverheadBytes = 1 + 1 + 1 + 4 + 6 + 1;
+const int _sendChannelTextMsgOverheadBytes = 1 + 1 + 1 + 4 + 1;
+
+int maxContactMessageBytes() {
+  final byFrame = maxFrameSize - _sendTextMsgOverheadBytes;
+  return _minPositive(byFrame, maxTextPayloadBytes);
+}
+
+int maxChannelMessageBytes(String? senderName) {
+  final nameLength = _senderNameBytes(senderName);
+  final prefixBytes = nameLength + 2; // "<name>: "
+  final byPayload = maxTextPayloadBytes - prefixBytes;
+  final byFrame = maxFrameSize - _sendChannelTextMsgOverheadBytes;
+  return _minPositive(byPayload, byFrame);
+}
+
+int _senderNameBytes(String? senderName) {
+  if (senderName == null || senderName.isEmpty) return maxNameSize - 1;
+  final bytes = utf8.encode(senderName);
+  final maxBytes = maxNameSize - 1;
+  return bytes.length > maxBytes ? maxBytes : bytes.length;
+}
+
+int _minPositive(int a, int b) {
+  final minValue = a < b ? a : b;
+  return minValue < 0 ? 0 : minValue;
+}
 
 // Contact frame offsets
 const int contactPubKeyOffset = 1;
@@ -295,12 +324,16 @@ Uint8List buildRemoveContactFrame(Uint8List pubKey) {
 }
 
 // Build CMD_APP_START frame
-// Format: [cmd][reserved x7][app_name...]
-Uint8List buildAppStartFrame({String appName = 'MeshCoreOpen'}) {
+// Format: [cmd][app_ver][reserved x6][app_name...]
+Uint8List buildAppStartFrame({
+  String appName = 'MeshCoreOpen',
+  int appVersion = 1,
+}) {
   final nameBytes = utf8.encode(appName);
   final frame = Uint8List(8 + nameBytes.length + 1);
   frame[0] = cmdAppStart;
-  // bytes 1-7 are reserved (zeros)
+  frame[1] = appVersion;
+  // bytes 2-7 are reserved (zeros)
   frame.setRange(8, 8 + nameBytes.length, nameBytes);
   frame[frame.length - 1] = 0; // null terminator
   return frame;