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

push_notifications/lib/main.dart

@@ -4,6 +4,8 @@ import 'package:flutter/material.dart';
 void main() => runApp(MyApp());
 
 class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
@@ -18,6 +20,8 @@ class MyApp extends StatelessWidget {
 }
 
 class MyHomePage extends StatefulWidget {
+  const MyHomePage({super.key});
+
   @override
   _MyHomePageState createState() => _MyHomePageState();
 }
@@ -86,7 +90,7 @@ and other fields as per requirement
           child: Column(
             children: <Widget>[
               Text(
-                '$title',
+                title,
                 style: Theme.of(context).textTheme.headlineSmall,
               ),
               SizedBox(