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

stateful_widget/lib/main.dart

@@ -7,6 +7,8 @@ void main() {
 }
 
 class MyButton extends StatefulWidget {
+  const MyButton({super.key});
+
   @override
   MyButtonState createState() {
     return MyButtonState();
@@ -40,12 +42,12 @@ class MyButtonState extends State<MyButton> {
               Text(displayedString, style: TextStyle(fontSize: 40.0)),
               Padding(padding: EdgeInsets.all(10.0)),
               ElevatedButton(
+                style: ElevatedButton.styleFrom(backgroundColor: Colors.red),
+                onPressed: onPressOfButton,
                 child: Text(
                   "Press me",
                   style: TextStyle(color: Colors.white),
                 ),
-                style: ElevatedButton.styleFrom(backgroundColor: Colors.red),
-                onPressed: onPressOfButton,
               )
             ],
           ),