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/analysis_options.yaml

@@ -0,0 +1,23 @@
+# Lint rules for Flutter apps.
+# See https://dart.dev/guides/language/analysis-options
+include: package:flutter_lints/flutter.yaml
+
+analyzer:
+  exclude:
+    - build/**
+    - android/**
+    - ios/**
+    - web/**
+    - windows/**
+    - macos/**
+    - linux/**
+
+linter:
+  rules:
+    # Noise in small sample apps; keep the code readable.
+    avoid_print: false
+    avoid_unnecessary_containers: false
+    file_names: false
+    library_private_types_in_public_api: false
+    non_constant_identifier_names: false
+    strict_top_level_inference: false

unit_testing/android/app/src/main/AndroidManifest.xml

@@ -11,6 +11,7 @@
         android:icon="@mipmap/ic_launcher">
         <activity
             android:name="io.flutter.embedding.android.FlutterActivity"
+            android:exported="true"
             android:launchMode="singleTop"
             android:theme="@style/LaunchTheme"
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"

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();
 }

unit_testing/pubspec.yaml

@@ -32,6 +32,7 @@ dependencies:
 dev_dependencies:
   flutter_test:
     sdk: flutter
+  flutter_lints: ^6.0.0
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec