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/active_fires.dart

@@ -113,10 +113,11 @@ class _ActiveFiresPageState extends State<ActiveFiresPage> {
                 : Icons.notifications_off),
             color: loc.subscribed ? fires600 : null,
             onPressed: () {
-              loc.subscribed = !loc.subscribed;
-              onToggle(loc);
+              final YourLocation updatedLoc =
+                  loc.copyWith(subscribed: !loc.subscribed);
+              onToggle(updatedLoc);
               setState(() {});
-              showSnackMsg(loc.subscribed
+              showSnackMsg(updatedLoc.subscribed
                   ? S.of(context).subscribedToFires
                   : S.of(context).unsubscribedToFires);
             }),