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

unit_testing/lib/components/place_info_card.dart

@@ -3,7 +3,7 @@ import 'package:unit_testing/model/location.dart';
 
 class PlaceInfo extends StatelessWidget {
   final Location data;
-  PlaceInfo({required this.data});
+  const PlaceInfo({super.key, required this.data});
 
   @override
   Widget build(BuildContext context) {
@@ -26,7 +26,7 @@ class PlaceInfo extends StatelessWidget {
         crossAxisAlignment: CrossAxisAlignment.center,
         children: [
           Text(
-            data.name + "\n" + data.country,
+            "${data.name}\n${data.country}",
             style: TextStyle(
               fontSize: 25,
               color: Colors.black,

unit_testing/lib/main.dart

@@ -5,6 +5,8 @@ import 'package:unit_testing/screens/sign_in_screen.dart';
 void main() => runApp(MyApp());
 
 class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
   @override
   Widget build(BuildContext context) {
     return MaterialApp(

unit_testing/lib/screens/home_screen.dart

@@ -5,6 +5,8 @@ import 'package:unit_testing/model/location.dart';
 import '../helpers.dart';
 
 class HomeScreen extends StatefulWidget {
+  const HomeScreen({super.key});
+
   @override
   _HomeScreenState createState() => _HomeScreenState();
 }

unit_testing/lib/screens/sign_in_screen.dart

@@ -2,6 +2,8 @@ import 'package:flutter/material.dart';
 import 'package:unit_testing/helpers.dart';
 
 class SignInScreen extends StatefulWidget {
+  const SignInScreen({super.key});
+
   @override
   _SignInScreenState createState() => _SignInScreenState();
 }