Migrate fires_flutter to flutter_map v6.1.0 and complete major null-safety fixes

- Updated Android build files: gradle plugin 8.2.2, gradle 8.3, SDK 34, minSdk 21
- Ran dart fix --apply for 87 automatic null-safety fixes
- Migrated flutter_map v6 API breaking changes:
  - MapOptions: center → initialCenter, zoom → initialZoom
  - layers → children structure
  - TileLayerOptions/MarkerLayerOptions/PolylineLayerOptions → TileLayer/MarkerLayer/PolylineLayer
  - Removed plugin_api.dart imports
  - Converted old plugin system (ZoomMapPlugin, AttributionPlugin, etc.) to direct widgets
  - Updated onTap callback signature: (TapPosition) → (TapPosition, LatLng)
- Migrated all marker/polyline creation to v6 API
- Fixed FlatButton → TextButton deprecation
- Fixed stackTrace access with catch(e, stackTrace) pattern
- Removed deprecated flutter_google_places_autocomplete dependency
- Removed deprecated dependencies: latlong, connectivity, launch_review
- Updated all imports from latlong → latlong2
- Placeholder implementation for places autocomplete (feature temporarily disabled)

Remaining tasks (non-blocking for build):
- Complete null-safety fixes for _location variables in genericMap.dart
- Fix theme.dart MaterialTheme parameter issues
- Fix customStepper.dart null-safety issues
- Final build and testing

lib/models/appState.dart

@@ -52,12 +52,12 @@ class AppState {
       _$AppStateFromJson(json);
 
   AppState(
-      {this.yourLocations: const <YourLocation>[],
-      this.fireNotifications: const <FireNotification>[],
-      this.fireNotificationsUnread: 0,
-      this.user: const User.initial(),
-      this.isLoading: false,
-      this.isLoaded: false,
+      {this.yourLocations = const <YourLocation>[],
+      this.fireNotifications = const <FireNotification>[],
+      this.fireNotificationsUnread = 0,
+      this.user = const User.initial(),
+      this.isLoading = false,
+      this.isLoaded= false,
       this.error,
       this.gmapKey,
       this.firesApiKey,
@@ -65,7 +65,7 @@ class AppState {
       this.serverUrl,
       this.connectivity,
       this.monitoredAreas,
-      this.fireMapState: const FireMapState.initial()});
+      this.fireMapState = const FireMapState.initial()});
 
   AppState copyWith(
       {bool isLoading,