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

statless_counter_app/lib/counter.g.dart

@@ -6,7 +6,7 @@ part of 'counter.dart';
 // StoreGenerator
 // **************************************************************************
 
-// ignore_for_file: non_constant_identifier_names, unnecessary_brace_in_string_interps, unnecessary_lambdas, prefer_expression_function_bodies, lines_longer_than_80_chars, avoid_as, avoid_annotating_with_dynamic
+// ignore_for_file: non_constant_identifier_names, unnecessary_brace_in_string_interps, unnecessary_lambdas, prefer_expression_function_bodies, lines_longer_than_80_chars, avoid_as, avoid_annotating_with_dynamic, no_leading_underscores_for_local_identifiers
 
 mixin _$Counter on _Counter, Store {
   final _$valueAtom = Atom(name: '_Counter.value');

statless_counter_app/lib/main.dart

@@ -8,6 +8,8 @@ final counter = Counter(); // Instantiate the store
 void main() => runApp(MyApp());
 
 class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
   // This widget is the root of your application.
   @override
   Widget build(BuildContext context) {
@@ -23,7 +25,7 @@ class MyApp extends StatelessWidget {
 }
 
 class MyHomePage extends StatelessWidget {
-  const MyHomePage();
+  const MyHomePage({super.key});
 
   @override
   Widget build(BuildContext context) {