Fix linting issues and code quality improvements

Resolve 62 linting issues identified by flutter analyze, reducing
total issues from 79 to 17. All critical warnings addressed.

Changes:
- Replace deprecated withOpacity() with withValues(alpha:) (25 instances)
- Remove unused imports from 9 files
- Remove unused variables and fields (6 instances)
- Fix Riverpod 3.0 state access violations in settings_page
- Remove unnecessary null-aware operators in navigation_page (6 instances)
- Fix unnecessary type casts in providers (4 instances)
- Remove unused methods: _getDarkMapStyle, _showPermissionDialog
- Simplify hover state management by removing unused _isHovered fields

Remaining 17 issues are info-level style suggestions and defensive
programming patterns that don't impact functionality.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/pages/navigation_page.dart

@@ -4,7 +4,6 @@ import 'package:google_navigation_flutter/google_navigation_flutter.dart';
 import 'package:planb_logistic/l10n/app_localizations.dart';
 import '../models/delivery.dart';
 import '../services/location_permission_service.dart';
-import '../components/navigation_tc_dialog.dart';
 
 class NavigationPage extends ConsumerStatefulWidget {
   final Delivery delivery;
@@ -139,38 +138,6 @@ class _NavigationPageState extends ConsumerState<NavigationPage> {
     }
   }
 
-  void _showPermissionDialog() {
-    final l10n = AppLocalizations.of(context);
-
-    showDialog(
-      context: context,
-      barrierDismissible: false,
-      builder: (context) => AlertDialog(
-        title: Text(l10n?.locationPermissionRequired ?? 'Location Permission'),
-        content: Text(
-          l10n?.locationPermissionMessage ??
-              'This app requires location permission to navigate to deliveries.',
-        ),
-        actions: [
-          TextButton(
-            onPressed: () {
-              Navigator.of(context).pop();
-              widget.onNavigationCancelled?.call();
-            },
-            child: Text(l10n?.cancel ?? 'Cancel'),
-          ),
-          TextButton(
-            onPressed: () {
-              Navigator.of(context).pop();
-              _requestLocationPermission();
-            },
-            child: Text(l10n?.requestPermission ?? 'Request Permission'),
-          ),
-        ],
-      ),
-    );
-  }
-
   Future<void> _requestLocationPermission() async {
     final result = await _permissionService.requestLocationPermission();
 
@@ -206,22 +173,19 @@ class _NavigationPageState extends ConsumerState<NavigationPage> {
     showDialog(
       context: context,
       builder: (context) => AlertDialog(
-        title: Text(l10n?.permissionPermanentlyDenied ?? 'Permission Required'),
-        content: Text(
-          l10n?.openSettingsMessage ??
-              'Location permission is permanently denied. Please enable it in app settings.',
-        ),
+        title: Text(l10n.permissionPermanentlyDenied),
+        content: Text(l10n.openSettingsMessage),
         actions: [
           TextButton(
             onPressed: () => Navigator.of(context).pop(),
-            child: Text(l10n?.cancel ?? 'Cancel'),
+            child: Text(l10n.cancel),
           ),
           TextButton(
             onPressed: () {
               _permissionService.openAppSettings();
               Navigator.of(context).pop();
             },
-            child: Text(l10n?.openSettings ?? 'Open Settings'),
+            child: Text(l10n.openSettings),
           ),
         ],
       ),
@@ -389,7 +353,7 @@ class _NavigationPageState extends ConsumerState<NavigationPage> {
     return Scaffold(
       appBar: AppBar(
         title: Text(
-          '${l10n?.navigatingTo ?? 'Navigating to'}: ${widget.delivery.name}',
+          '${l10n.navigatingTo}: ${widget.delivery.name}',
         ),
         elevation: 0,
       ),
@@ -417,10 +381,7 @@ class _NavigationPageState extends ConsumerState<NavigationPage> {
                 children: [
                   const CircularProgressIndicator(),
                   const SizedBox(height: 16),
-                  Text(
-                    l10n?.initializingNavigation ??
-                        'Initializing navigation...',
-                  ),
+                  Text(l10n.initializingNavigation),
                 ],
               ),
             ),