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/services/app_debug_log_service.dart

@@ -0,0 +1,92 @@
+import 'package:flutter/foundation.dart';
+
+enum AppDebugLogLevel {
+  info,
+  warning,
+  error,
+}
+
+class AppDebugLogEntry {
+  final DateTime timestamp;
+  final AppDebugLogLevel level;
+  final String tag;
+  final String message;
+
+  AppDebugLogEntry({
+    required this.timestamp,
+    required this.level,
+    required this.tag,
+    required this.message,
+  });
+
+  String get levelLabel {
+    switch (level) {
+      case AppDebugLogLevel.info:
+        return 'INFO';
+      case AppDebugLogLevel.warning:
+        return 'WARN';
+      case AppDebugLogLevel.error:
+        return 'ERROR';
+    }
+  }
+
+  String get formattedTime {
+    return '${timestamp.hour.toString().padLeft(2, '0')}:'
+        '${timestamp.minute.toString().padLeft(2, '0')}:'
+        '${timestamp.second.toString().padLeft(2, '0')}.'
+        '${timestamp.millisecond.toString().padLeft(3, '0')}';
+  }
+}
+
+class AppDebugLogService extends ChangeNotifier {
+  static const int maxEntries = 1000;
+  final List<AppDebugLogEntry> _entries = [];
+  bool _enabled = false;
+
+  List<AppDebugLogEntry> get entries => List.unmodifiable(_entries);
+  bool get enabled => _enabled;
+
+  void setEnabled(bool value) {
+    _enabled = value;
+    notifyListeners();
+  }
+
+  void log(String message, {String tag = 'App', AppDebugLogLevel level = AppDebugLogLevel.info}) {
+    if (!_enabled) return;
+
+    _entries.add(
+      AppDebugLogEntry(
+        timestamp: DateTime.now(),
+        level: level,
+        tag: tag,
+        message: message,
+      ),
+    );
+
+    if (_entries.length > maxEntries) {
+      _entries.removeRange(0, _entries.length - maxEntries);
+    }
+
+    notifyListeners();
+
+    // Also print to console for development
+    debugPrint('[$tag] $message');
+  }
+
+  void info(String message, {String tag = 'App'}) {
+    log(message, tag: tag, level: AppDebugLogLevel.info);
+  }
+
+  void warn(String message, {String tag = 'App'}) {
+    log(message, tag: tag, level: AppDebugLogLevel.warning);
+  }
+
+  void error(String message, {String tag = 'App'}) {
+    log(message, tag: tag, level: AppDebugLogLevel.error);
+  }
+
+  void clear() {
+    _entries.clear();
+    notifyListeners();
+  }
+}