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

stateless_widgets/lib/main.dart

@@ -9,6 +9,8 @@ void main() {
 }
 
 class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
   @override
   Widget build(BuildContext context) {
     // Declare some constants
@@ -64,7 +66,6 @@ class MyApp extends StatelessWidget {
         ),
       ),
     );
-    ;
   }
 }
 
@@ -74,7 +75,7 @@ class MyCard extends StatelessWidget {
   final Widget title;
 
   // Constructor. {} here denote that they are optional values i.e you can use as: MyCard()
-  MyCard({required this.title, required this.icon});
+  const MyCard({super.key, required this.title, required this.icon});
 
   @override
   Widget build(BuildContext context) {
@@ -84,7 +85,7 @@ class MyCard extends StatelessWidget {
         child: Container(
           padding: const EdgeInsets.all(20.0),
           child: Column(
-            children: <Widget>[this.title, this.icon],
+            children: <Widget>[title, icon],
           ),
         ),
       ),