refactor: standardize Dart and Android config across all 54 apps

- Bump all apps to sdk >=3.0.0 <4.0.0 and add flutter_lints + a shared
  analysis_options.yaml to every app (flutter analyze is now green repo-wide)
- Fix real compile errors in firebase_google_authentication and image_editor,
  plus deprecated APIs (Matrix4, SvgPicture.color, textScaleFactor),
  missing async 'mounted' guards, and misc lints via dart fix + manual fixes
- Align pubspec 'name' with each folder and Android namespace/applicationId
  with the documented github.nisrulz.* convention
- Convert bmi_calculator from a legacy Flutter module to a standard app
  with a proper android/ scaffold; fix missing android:exported in launcher
  manifests across 22 apps so all Android builds pass
- Untrack generated build files (GeneratedPluginRegistrant,
  .flutter-plugins-dependencies) and ignore them

grid_layout/lib/gridview.dart

@@ -14,7 +14,7 @@ class MyGridView {
             mainAxisSize: MainAxisSize.min,
             verticalDirection: VerticalDirection.down,
             children: <Widget>[
-              Image(image: AssetImage('data_repo/img/' + image)),
+              Image(image: AssetImage('data_repo/img/$image')),
               Center(
                 child: Text(name),
               )

grid_layout/lib/main.dart

@@ -6,6 +6,8 @@ void main() => runApp(MyApp());
 class MyApp extends StatelessWidget {
   final MyGridView myGridView = MyGridView();
 
+  MyApp({super.key});
+
   @override
   Widget build(BuildContext context) {
     return MaterialApp(