Add advanced path management, debug logging, and fix channel sync

New features:
- In-app debug log viewer with copy/clear functionality
- Advanced path management UI with history and custom path builder
- Battery indicator widget with voltage/percentage toggle
- Contact/channel filtering and sorting improvements
- Repeater command ACK tracking with path history integration

Fixes:
- Switch channel sync from parallel to sequential to prevent timeouts
- Preserve path overrides when contacts refresh from device
- Fix ACK hash computation for SMAZ-encoded messages
- Proper cleanup of pending operations on disconnect

lib/screens/device_screen.dart

@@ -39,10 +39,17 @@ class _DeviceScreenState extends State<DeviceScreen>
           canPop: false,
           child: Scaffold(
             appBar: AppBar(
+              leading: _buildBatteryIndicator(connector, context),
               titleSpacing: 16,
               centerTitle: false,
               title: _buildAppBarTitle(connector, theme),
+              automaticallyImplyLeading: false,
               actions: [
+                IconButton(
+                  icon: const Icon(Icons.bluetooth_disabled),
+                  tooltip: 'Disconnect',
+                  onPressed: () => _disconnect(context, connector),
+                ),
                 IconButton(
                   icon: const Icon(Icons.tune),
                   tooltip: 'Settings',
@@ -53,11 +60,6 @@ class _DeviceScreenState extends State<DeviceScreen>
                     ),
                   ),
                 ),
-                IconButton(
-                  icon: const Icon(Icons.bluetooth_disabled),
-                  tooltip: 'Disconnect',
-                  onPressed: () => _disconnect(context, connector),
-                ),
               ],
             ),
             body: SafeArea(