Fix Firebase initialization error - no-app exception

- Add Firebase.initializeApp() call in mainCommon.dart before any Firebase-dependent code
- Make mainCommon() async to support await Firebase.initializeApp()
- Update mainDev.dart to properly await mainCommon() call
- Add android:enableOnBackInvokedCallback='true' to AndroidManifest.xml to fix OnBackInvokedCallback warning

This resolves the 'No Firebase App [DEFAULT] has been created' error that was occurring when firebase_messaging tried to access FirebaseMessaging.instance in homePage.dart. Firebase must be initialized before any Firebase APIs are used.

lib/mainCommon.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 
 import 'package:comunes_flutter/comunes_flutter.dart';
+import 'package:firebase_core/firebase_core.dart';
 import 'package:flutter/material.dart';
 import 'package:get_it/get_it.dart';
 import 'package:package_info_plus/package_info_plus.dart';
@@ -27,8 +28,12 @@ Future<Map<String, dynamic>> loadSecrets() async {
       .load();
 }
 
-void mainCommon(List<Middleware<AppState>> otherMiddleware) {
+Future<void> mainCommon(List<Middleware<AppState>> otherMiddleware) async {
   WidgetsFlutterBinding.ensureInitialized();
+
+  // Initialize Firebase before any Firebase-dependent code runs
+  await Firebase.initializeApp();
+
   final getIt = GetIt.instance;
   getIt.registerSingleton<FiresApi>(FiresApi());
   loadPackageInfo().then((packageInfo) {

lib/mainDev.dart

@@ -24,5 +24,5 @@ void main() async {
       logRedux == LogLevel.actions ? [] : [createLoggingMiddleware()];
 
   // In development, Sentry is disabled, so we skip initialization
-  mainCommon(devMiddlewares);
+  await mainCommon(devMiddlewares);
 }