fix: reduce pairing dialog frequency by adding readable permission and implementing 5m handshake backoff

Author: CreatorJohn

lib/src/features/discovery/data/ble_advertiser.dart

@@ -166,11 +166,15 @@ class BLEAdvertiser {
             BleCharacteristic(
               uuid: messageCharUuid,
               properties: [
+                CharacteristicProperties.read.index,
                 CharacteristicProperties.write.index,
                 CharacteristicProperties.notify.index,
                 CharacteristicProperties.indicate.index,
               ],
-              permissions: [AttributePermissions.writeable.index],
+              permissions: [
+                AttributePermissions.readable.index,
+                AttributePermissions.writeable.index,
+              ],
               value: Uint8List.fromList([0x00]),
             ),
           ],

lib/src/features/discovery/data/ble_discoverer.dart

@@ -26,6 +26,7 @@ class BLEDiscoverer {
   final Logger _log = Logger('BLEDiscoverer');
   final Map<int, BluetoothDevice> _syncQueue = {};
   final Map<int, DateTime> _lastSyncAttempt = {};
+  final Map<int, DateTime> _lastHandshakeAttempt = {};
   final Set<int> _activeSyncs = {};
 
   final StreamController<bool> _scanStatusController = StreamController.broadcast();
@@ -296,7 +297,16 @@ class BLEDiscoverer {
             Duration(milliseconds: 1000 + Random().nextInt(2000)),
           );
           _lastSyncAttempt[entry.key] = DateTime.now();
+          
+          final lastHandshake = _lastHandshakeAttempt[entry.key];
+          if (lastHandshake != null && 
+              DateTime.now().difference(lastHandshake).inMinutes < 5) {
+            _log.info('Skipping full sync for ${entry.key} due to backoff');
+            continue;
+          }
+
           _activeSyncs.add(entry.key);
+          _lastHandshakeAttempt[entry.key] = DateTime.now();
 
           service.invoke('updateProgress', {
             'value': 1.0,