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

expense_planner/lib/widgets/new_transaction.dart

@@ -4,7 +4,7 @@ import 'package:intl/intl.dart';
 class NewTransaction extends StatefulWidget {
   final Function addTx;
 
-  NewTransaction(this.addTx);
+  const NewTransaction(this.addTx, {super.key});
 
   @override
   _NewTransactionState createState() => _NewTransactionState();
@@ -72,7 +72,7 @@ class _NewTransactionState extends State<NewTransaction> {
               keyboardType: TextInputType.number,
               onSubmitted: (_) => _submitData(),
             ),
-            Container(
+            SizedBox(
               height: 70,
               child: Row(
                 children: <Widget>[