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

stateless_widgets/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

stateless_widgets/lib/main.dart

@@ -9,6 +9,8 @@ void main() {
 }
 
 class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
   @override
   Widget build(BuildContext context) {
     // Declare some constants
@@ -64,7 +66,6 @@ class MyApp extends StatelessWidget {
         ),
       ),
     );
-    ;
   }
 }
 
@@ -74,7 +75,7 @@ class MyCard extends StatelessWidget {
   final Widget title;
 
   // Constructor. {} here denote that they are optional values i.e you can use as: MyCard()
-  MyCard({required this.title, required this.icon});
+  const MyCard({super.key, required this.title, required this.icon});
 
   @override
   Widget build(BuildContext context) {
@@ -84,7 +85,7 @@ class MyCard extends StatelessWidget {
         child: Container(
           padding: const EdgeInsets.all(20.0),
           child: Column(
-            children: <Widget>[this.title, this.icon],
+            children: <Widget>[title, icon],
           ),
         ),
       ),

stateless_widgets/pubspec.yaml

@@ -11,6 +11,7 @@ dependencies:
 dev_dependencies:
   flutter_test:
     sdk: flutter
+  flutter_lints: ^6.0.0
 
 
 # For information on the generic Dart part of this file, see the