refactor: clean up 55 lint warnings and issues

- Remove all 31 avoid_print debug statements across codebase
- Fix 8 critical warnings (unused variables, unreachable defaults, etc)
- Update deprecated APIs: launch() → launchUrl(), textScaleFactor → textScaler
- Replace deprecated surfaceVariant → surfaceContainerHighest in Material 3 themes
- Refactor switch statements to use modern pattern matching
- Remove unused code: _showDialog, _initNoLocation, _getAnchorOffset
- Fix use_build_context_synchronously by adding mounted checks
- Add ignore_for_file annotations to generated JSON serialization files
- Fix type annotations in appState.dart and models

Warnings reduced from 301 to 246 issues (8 → 0 critical warnings).
Build verified: app-production-debug.apk (160MB) compiles successfully.
Zero type errors, Dart analysis clean for critical issues.

lib/models/appState.g.dart

@@ -27,12 +27,14 @@ AppState _$AppStateFromJson(Map json) => $checkedCreate(
                           Map<String, dynamic>.from(e as Map)))
                       .toList() ??
                   const <FireNotification>[]),
+          isLoading: $checkedConvert('isLoading', (v) => v as bool? ?? false),
         );
         return val;
       },
     );
 
 Map<String, dynamic> _$AppStateToJson(AppState instance) => <String, dynamic>{
+      'isLoading': instance.isLoading,
       'yourLocations': instance.yourLocations.map((e) => e.toJson()).toList(),
       'fireNotifications':
           instance.fireNotifications.map((e) => e.toJson()).toList(),