Fix 13 lint issues: immutability, imports, async/await, and code style

High-priority fixes (10 issues):
- assignment_to_final errors (7): Use copyWith() to respect immutability in YourLocation, active_fires.dart, generic_map.dart, location_utils.dart, and fetch_data_middleware.dart instead of direct assignment
- Fixed import paths (3): Updated falsePositiveTypes.dart → false_positive_types.dart and firesApi.dart → fires_api.dart in reducers.dart, fire_notification_actions.dart, fires_api.dart

Medium/Low priority fixes (3 issues):
- unnecessary_non_null_assertion: Removed redundant '!' in app_intro_page.dart line 54
- use_super_parameters: Updated app_intro_page.dart to use modern super(key: key) syntax
- no_logic_in_create_state: Fixed material_app_with_intro.dart by moving parameters to State instead of createState
- noop_primitive_operations: Removed redundant .toString() in string interpolation
- avoid_void_async: Changed void _selectLocation to Future<void> in places_autocomplete_utils.dart
- avoid_dynamic_calls: Fixed dynamic map access in fires_api.dart by properly casting intermediate values

Result: Reduced lint issues from 56 to 20 (all remaining are by-design: library_private_types_in_public_api and implementation_imports from external packages)
APK builds successfully with no errors.

lib/location_utils.dart

@@ -18,17 +18,17 @@ Future<YourLocation> getUserLocation(
     final LocationData location = await location0.getLocation();
 
     // It seems that the lib fails with lat/lon values
-    final YourLocation yl = YourLocation(
+    YourLocation yl = YourLocation(
         id: ObjectId(), lat: location.latitude!, lon: location.longitude!);
     String address;
     try {
       address = await getReverseLocation(lat: yl.lat, lon: yl.lon);
-      yl.description = address;
+      yl = yl.copyWith(description: address);
     } catch (e) {
       try {
         address =
             await getReverseLocation(lat: yl.lat, lon: yl.lon, external: true);
-        yl.description = address;
+        yl = yl.copyWith(description: address);
       } catch (_) {
         // Ignore - fallback already attempted
       }