🔄 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/screens/contacts_screen.dart

@@ -7,6 +7,7 @@ import '../models/contact.dart';
 import '../models/contact_group.dart';
 import '../storage/contact_group_store.dart';
 import '../widgets/repeater_login_dialog.dart';
+import '../widgets/unread_badge.dart';
 import '../utils/emoji_utils.dart';
 import 'chat_screen.dart';
 import 'repeater_hub_screen.dart';
@@ -29,6 +30,7 @@ class _ContactsScreenState extends State<ContactsScreen> {
   final TextEditingController _searchController = TextEditingController();
   String _searchQuery = '';
   ContactSortOption _sortOption = ContactSortOption.lastSeen;
+  bool _showUnreadOnly = false;
   final ContactGroupStore _groupStore = ContactGroupStore();
   List<ContactGroup> _groups = [];
 
@@ -166,6 +168,18 @@ class _ContactsScreenState extends State<ContactsScreen> {
               ),
             ],
           ),
+          IconButton(
+            icon: Icon(
+              Icons.mark_chat_unread_outlined,
+              color: _showUnreadOnly ? Theme.of(context).primaryColor : null,
+            ),
+            tooltip: _showUnreadOnly ? 'Showing unread only' : 'Show unread only',
+            onPressed: () {
+              setState(() {
+                _showUnreadOnly = !_showUnreadOnly;
+              });
+            },
+          ),
           IconButton(
             icon: const Icon(Icons.group_add),
             tooltip: 'New group',
@@ -222,7 +236,8 @@ class _ContactsScreenState extends State<ContactsScreen> {
           }
 
           final filteredAndSorted = _filterAndSortContacts(contacts, connector);
-          final filteredGroups = _filterAndSortGroups(_groups, contacts);
+          final filteredGroups =
+              _showUnreadOnly ? const <ContactGroup>[] : _filterAndSortGroups(_groups, contacts);
 
           return Column(
             children: [
@@ -265,7 +280,9 @@ class _ContactsScreenState extends State<ContactsScreen> {
                             Icon(Icons.search_off, size: 64, color: Colors.grey[400]),
                             const SizedBox(height: 16),
                             Text(
-                              'No contacts or groups found',
+                              _showUnreadOnly
+                                  ? 'No unread contacts'
+                                  : 'No contacts or groups found',
                               style: TextStyle(fontSize: 16, color: Colors.grey[600]),
                             ),
                           ],
@@ -281,8 +298,10 @@ class _ContactsScreenState extends State<ContactsScreen> {
                               return _buildGroupTile(context, group, contacts);
                             }
                             final contact = filteredAndSorted[index - filteredGroups.length];
+                            final unreadCount = connector.getUnreadCountForContact(contact);
                             return _ContactTile(
                               contact: contact,
+                              unreadCount: unreadCount,
                               onTap: () => _openChat(context, contact),
                               onLongPress: () => _showContactOptions(context, connector, contact),
                             );
@@ -324,6 +343,12 @@ class _ContactsScreenState extends State<ContactsScreen> {
       return contact.name.toLowerCase().contains(_searchQuery);
     }).toList();
 
+    if (_showUnreadOnly) {
+      filtered = filtered.where((contact) {
+        return connector.getUnreadCountForContact(contact) > 0;
+      }).toList();
+    }
+
     switch (_sortOption) {
       case ContactSortOption.lastSeen:
         filtered.sort((a, b) => b.lastSeen.compareTo(a.lastSeen));
@@ -399,6 +424,7 @@ class _ContactsScreenState extends State<ContactsScreen> {
     if (contact.type == advTypeRepeater) {
       _showRepeaterLogin(context, contact);
     } else {
+      context.read<MeshCoreConnector>().markContactRead(contact.publicKeyHex);
       Navigator.push(
         context,
         MaterialPageRoute(builder: (context) => ChatScreen(contact: contact)),
@@ -702,11 +728,13 @@ class _ContactsScreenState extends State<ContactsScreen> {
 
 class _ContactTile extends StatelessWidget {
   final Contact contact;
+  final int unreadCount;
   final VoidCallback onTap;
   final VoidCallback onLongPress;
 
   const _ContactTile({
     required this.contact,
+    required this.unreadCount,
     required this.onTap,
     required this.onLongPress,
   });
@@ -724,6 +752,10 @@ class _ContactTile extends StatelessWidget {
         mainAxisAlignment: MainAxisAlignment.center,
         crossAxisAlignment: CrossAxisAlignment.end,
         children: [
+          if (unreadCount > 0) ...[
+            UnreadBadge(count: unreadCount),
+            const SizedBox(height: 4),
+          ],
           Text(
             _formatLastSeen(contact.lastSeen),
             style: TextStyle(fontSize: 12, color: Colors.grey[600]),