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/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

view_pdf_file/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"

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,
   });
 

view_pdf_file/pubspec.yaml

@@ -31,6 +31,7 @@ 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