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/yourLocation.dart

@@ -7,7 +7,6 @@ part 'yourLocation.g.dart';
 
 @JsonSerializable(nullable: false)
 class YourLocation {
-
   YourLocation(
       {required this.id,
       required this.lat,
@@ -33,10 +32,6 @@ class YourLocation {
   static late final YourLocation noLocation;
   static const int? withoutStats = null;
 
-  static void _initNoLocation() {
-    noLocation = YourLocation(
-        id: ObjectId(), lat: 0.0, lon: 0.0);
-  }
   Map<String, dynamic> toJson() => _$YourLocationToJson(this);
 
   YourLocation copyWith(