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

view_pdf_file/lib/main.dart

@@ -8,6 +8,8 @@ void main() {
 }
 
 class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
@@ -21,6 +23,8 @@ class MyApp extends StatelessWidget {
 }
 
 class HomePage extends StatefulWidget {
+  const HomePage({super.key});
+
   @override
   _HomePageState createState() => _HomePageState();
 }
@@ -63,7 +67,7 @@ class _HomePageState extends State<HomePage> {
     );
   }
 
-  loadFromAsset() async {
+  Future<void> loadFromAsset() async {
     setState(() {
       isLoading = true;
     });
@@ -79,7 +83,7 @@ class _HomePageState extends State<HomePage> {
     );
   }
 
-  loadFromURL() async {
+  Future<void> loadFromURL() async {
     setState(() {
       isLoading = true;
     });

view_pdf_file/lib/viewPDF.dart

@@ -2,7 +2,7 @@ import 'package:flutter/material.dart';
 
 class ViewPDF extends StatelessWidget {
   final Widget viewer;
-  ViewPDF({
+  const ViewPDF({super.key, 
     required this.viewer,
   });