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

load_local_image/lib/main.dart

@@ -7,6 +7,8 @@ void main() {
 }
 
 class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -14,19 +16,18 @@ class MyApp extends StatelessWidget {
           title: Text("Load local image"),
         ),
         body: Container(
-          child: Center(
-            child: Text(
-              "Hello World!",
-              style: TextStyle(color: Colors.white),
-            ),
-          ),
-          // Set the image as the background of the Container
           decoration: BoxDecoration(
               image: DecorationImage(
                   // Load image from assets
                   image: AssetImage('data_repo/img/bg1.jpg'),
                   // Make the image cover the whole area
                   fit: BoxFit.cover)),
+          child: Center(
+            child: Text(
+              "Hello World!",
+              style: TextStyle(color: Colors.white),
+            ),
+          ),
         ));
   }
 }