feat(firebase): integrate Firebase + APNs/FCM push notifications

Phase 2 of multi-environment setup. Adds Firebase core, Crashlytics,
Analytics, Remote Config, Performance, Messaging and flutter_local_notifications,
plus full APNs configuration for iOS push.

- Wire setupFirebase(env) and setupNotifications() in initApp
- Add firebase_options for dev and staging via flutterfire (sf-platform-pre)
- Register google-services / firebase-perf / crashlytics gradle plugins
- Add per-flavor GoogleService-Info.plist with Build Phase script that
  copies the right plist into the .app bundle based on \$CONFIGURATION
- Bump iOS deployment target 13.0 -> 15.0 (required by firebase_analytics)
- Pin flutter_local_notifications to ^19.4.2 (v20+ needs Dart SDK >=3.10)
- Add aps-environment to staging (development) and production entitlements;
  development flavor intentionally excluded (no App Store Connect entry)
- Fix AppDelegate.swift to call super.application after forwarding to
  AntelopAppDelegate, otherwise Firebase Messaging swizzling breaks and
  the APNs token is never captured
- Crashlytics reports in all builds (debug + release) for early detection
- Tag analytics events with env user property per flavor
- App Check intentionally not included (debug-token friction with large
  QA team); can be re-added release-only later

apps/mobile_app/lib/firebase_options_dev.dart

@@ -0,0 +1,68 @@
+// File generated by FlutterFire CLI.
+// ignore_for_file: type=lint
+import 'package:firebase_core/firebase_core.dart' show FirebaseOptions;
+import 'package:flutter/foundation.dart'
+    show defaultTargetPlatform, kIsWeb, TargetPlatform;
+
+/// Default [FirebaseOptions] for use with your Firebase apps.
+///
+/// Example:
+/// ```dart
+/// import 'firebase_options_dev.dart';
+/// // ...
+/// await Firebase.initializeApp(
+///   options: DefaultFirebaseOptions.currentPlatform,
+/// );
+/// ```
+class DefaultFirebaseOptions {
+  static FirebaseOptions get currentPlatform {
+    if (kIsWeb) {
+      throw UnsupportedError(
+        'DefaultFirebaseOptions have not been configured for web - '
+        'you can reconfigure this by running the FlutterFire CLI again.',
+      );
+    }
+    switch (defaultTargetPlatform) {
+      case TargetPlatform.android:
+        return android;
+      case TargetPlatform.iOS:
+        return ios;
+      case TargetPlatform.macOS:
+        throw UnsupportedError(
+          'DefaultFirebaseOptions have not been configured for macos - '
+          'you can reconfigure this by running the FlutterFire CLI again.',
+        );
+      case TargetPlatform.windows:
+        throw UnsupportedError(
+          'DefaultFirebaseOptions have not been configured for windows - '
+          'you can reconfigure this by running the FlutterFire CLI again.',
+        );
+      case TargetPlatform.linux:
+        throw UnsupportedError(
+          'DefaultFirebaseOptions have not been configured for linux - '
+          'you can reconfigure this by running the FlutterFire CLI again.',
+        );
+      default:
+        throw UnsupportedError(
+          'DefaultFirebaseOptions are not supported for this platform.',
+        );
+    }
+  }
+
+  static const FirebaseOptions android = FirebaseOptions(
+    apiKey: 'AIzaSyAzo8E_L6iUYWmK1BDFpNqRri1df6CqJiY',
+    appId: '1:535646668726:android:c3a09d6c26f0cdf95e6317',
+    messagingSenderId: '535646668726',
+    projectId: 'sf-platform-pre',
+    storageBucket: 'sf-platform-pre.firebasestorage.app',
+  );
+
+  static const FirebaseOptions ios = FirebaseOptions(
+    apiKey: 'AIzaSyBeijehJIznndwIUlbMkj6reYT4z-WHGfQ',
+    appId: '1:535646668726:ios:524afa641f61d7cb5e6317',
+    messagingSenderId: '535646668726',
+    projectId: 'sf-platform-pre',
+    storageBucket: 'sf-platform-pre.firebasestorage.app',
+    iosBundleId: 'com.savefamily.app.dev',
+  );
+}