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/locationUtils.dart

@@ -30,7 +30,6 @@ Future<YourLocation> getUserLocation(
             await getReverseLocation(lat: yl.lat, lon: yl.lon, external: true);
         yl.description = address;
       } catch (e) {
-        print('We cannot reverse geolocate');
       }
     }
     return yl;
@@ -59,13 +58,11 @@ Future<String> getReverseLocation(
       final geo.Placemark first = placemarks.first;
       final String address =
           '${first.street}, ${first.locality}, ${first.administrativeArea}, ${first.country}';
-      print('${first.name} : $address');
       return address;
     } else {
       return 'Unable to determine address';
     }
   } catch (e) {
-    print('Error in reverse geocoding: $e');
     throw Exception('Failed to reverse geocode: $e');
   }
 }