fix: Add mounted checks and fix memory leaks across UI components

Address potential memory leaks and state-after-dispose issues:

- AppProvider: Add dispose method to clean up listeners and callbacks
- MapTab: Store and restore original location callback instead of nullifying
- MessagesTab: Use Timer instead of Future.delayed for highlight cleanup
- ConnectionDialog: Use named listener method for proper tab controller cleanup
- RoomLoginSheet: Add _isDisposed flag to handle async callback race conditions
- SettingsScreen: Clear location service callbacks in dispose
- Various screens: Add mounted checks before setState after async operations
  (contacts_tab, device_config, home_screen, map_management, packet_log,
   sar_template_management, sar_update_sheet, permission_request_dialog)

lib/widgets/connection_dialog.dart

@@ -22,6 +22,26 @@ class _ConnectionDialogState extends State<ConnectionDialog>
   int _totalToScan = 0;
   String? _connectingToServerUrl; // Track which server is being connected to
 
+  // Named listener method for proper cleanup
+  void _onTabChanged() {
+    if (_tabController.index == 1) {
+      // Switched to network tab
+      if (_networkScanner.hasCachedResults && _discoveredServers.isEmpty) {
+        // Load cached results
+        setState(() {
+          _discoveredServers.addAll(_networkScanner.cachedServers);
+        });
+        debugPrint(
+          '📦 [NetworkScanner] Loaded ${_discoveredServers.length} servers from cache',
+        );
+      } else if (!_networkScanner.isScanning &&
+          !_networkScanner.hasCachedResults) {
+        // No cache, start initial scan
+        _startNetworkScan();
+      }
+    }
+  }
+
   @override
   void initState() {
     super.initState();
@@ -55,25 +75,8 @@ class _ConnectionDialogState extends State<ConnectionDialog>
       }
     };
 
-    // Listen to tab changes
-    _tabController.addListener(() {
-      if (_tabController.index == 1) {
-        // Switched to network tab
-        if (_networkScanner.hasCachedResults && _discoveredServers.isEmpty) {
-          // Load cached results
-          setState(() {
-            _discoveredServers.addAll(_networkScanner.cachedServers);
-          });
-          debugPrint(
-            '📦 [NetworkScanner] Loaded ${_discoveredServers.length} servers from cache',
-          );
-        } else if (!_networkScanner.isScanning &&
-            !_networkScanner.hasCachedResults) {
-          // No cache, start initial scan
-          _startNetworkScan();
-        }
-      }
-    });
+    // Listen to tab changes using named method for proper cleanup
+    _tabController.addListener(_onTabChanged);
   }
 
   @override
@@ -84,6 +87,8 @@ class _ConnectionDialogState extends State<ConnectionDialog>
     );
     connectionProvider.stopScan();
     _networkScanner.stopScan();
+    // Remove listener before disposing to prevent memory leaks
+    _tabController.removeListener(_onTabChanged);
     _tabController.dispose();
     super.dispose();
   }

lib/widgets/contacts/direct_message_sheet.dart

@@ -41,6 +41,7 @@ class _DirectMessageSheetState extends State<DirectMessageSheet> {
   }
 
   void _updateCharacterCount() {
+    if (!mounted) return;
     setState(() {
       _characterCount = _textController.text.length;
     });

lib/widgets/contacts/room_login_sheet.dart

@@ -21,6 +21,7 @@ class _RoomLoginSheetState extends State<RoomLoginSheet> {
   final FocusNode _focusNode = FocusNode();
   bool _isLoggingIn = false;
   bool _obscurePassword = true;
+  bool _isDisposed = false; // Track disposal state for async callbacks
 
   @override
   void initState() {
@@ -30,6 +31,7 @@ class _RoomLoginSheetState extends State<RoomLoginSheet> {
 
   @override
   void dispose() {
+    _isDisposed = true;
     _passwordController.dispose();
     _focusNode.dispose();
     super.dispose();
@@ -245,15 +247,15 @@ class _RoomLoginSheetState extends State<RoomLoginSheet> {
         '   Messages will be fetched when onMessageWaiting callback is triggered',
       );
 
-      if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(
-            content: Text(AppLocalizations.of(context)!.loggedInSuccessfully),
-            backgroundColor: Theme.of(context).colorScheme.primary,
-            duration: const Duration(seconds: 3),
-          ),
-        );
-      }
+      // Check both _isDisposed flag and mounted to handle race conditions
+      if (_isDisposed || !mounted) return;
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(
+          content: Text(AppLocalizations.of(context)!.loggedInSuccessfully),
+          backgroundColor: Theme.of(context).colorScheme.primary,
+          duration: const Duration(seconds: 3),
+        ),
+      );
     };
 
     connectionProvider.onLoginFail = (publicKeyPrefix) {
@@ -263,15 +265,15 @@ class _RoomLoginSheetState extends State<RoomLoginSheet> {
 
       debugPrint('❌ [RoomLogin] Login failed - incorrect password');
 
-      if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(
-            content: Text(AppLocalizations.of(context)!.loginFailed),
-            backgroundColor: Theme.of(context).colorScheme.error,
-            duration: const Duration(seconds: 3),
-          ),
-        );
-      }
+      // Check both _isDisposed flag and mounted to handle race conditions
+      if (_isDisposed || !mounted) return;
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(
+          content: Text(AppLocalizations.of(context)!.loginFailed),
+          backgroundColor: Theme.of(context).colorScheme.error,
+          duration: const Duration(seconds: 3),
+        ),
+      );
     };
 
     try {

lib/widgets/messages/sar_update_sheet.dart

@@ -231,6 +231,7 @@ class _SarUpdateSheetState extends State<SarUpdateSheet> {
     try {
       // Check if location services are enabled
       bool serviceEnabled = await Geolocator.isLocationServiceEnabled();
+      if (!mounted) return;
       if (!serviceEnabled) {
         setState(() {
           _locationError = 'Location services are disabled';
@@ -241,8 +242,10 @@ class _SarUpdateSheetState extends State<SarUpdateSheet> {
 
       // Check permissions
       LocationPermission permission = await Geolocator.checkPermission();
+      if (!mounted) return;
       if (permission == LocationPermission.denied) {
         permission = await Geolocator.requestPermission();
+        if (!mounted) return;
         if (permission == LocationPermission.denied) {
           setState(() {
             _locationError = 'Location permission denied';

lib/widgets/permission_request_dialog.dart

@@ -38,6 +38,7 @@ class _PermissionRequestDialogState extends State<PermissionRequestDialog> {
     try {
       // Check if location service is enabled
       final serviceEnabled = await Geolocator.isLocationServiceEnabled();
+      if (!mounted) return;
       if (!serviceEnabled) {
         setState(() {
           _errorMessage = 'Location services are disabled. Please enable location services in your device settings.';
@@ -48,10 +49,12 @@ class _PermissionRequestDialogState extends State<PermissionRequestDialog> {
 
       // Check current permission
       LocationPermission permission = await Geolocator.checkPermission();
+      if (!mounted) return;
 
       if (permission == LocationPermission.denied) {
         // Request permission
         permission = await Geolocator.requestPermission();
+        if (!mounted) return;
       }
 
       if (permission == LocationPermission.denied) {
@@ -78,11 +81,10 @@ class _PermissionRequestDialogState extends State<PermissionRequestDialog> {
       });
 
       // Close dialog and notify parent
-      if (mounted) {
-        Navigator.of(context).pop();
-        widget.onPermissionsGranted();
-      }
+      Navigator.of(context).pop();
+      widget.onPermissionsGranted();
     } catch (e) {
+      if (!mounted) return;
       setState(() {
         _errorMessage = 'Error requesting permissions: $e';
         _isRequesting = false;