feat(analytics): wire Firebase Analytics into app startup

flutterfire configure registered the iOS/Android apps under project
block-seasons and generated firebase_options.dart + native config. main()
now initializes Firebase and routes analytics through FirebaseAnalyticsBackend
in release builds (console logger in debug, so dev traffic never pollutes
GA4). Firebase init is guarded — failure falls back to the debug logger
rather than blocking startup.

firebase.json keeps the existing Hosting config and gains the FlutterFire
platform section. Client config files are committed (they ship in the binary;
Firebase security is enforced by rules, not config secrecy).

flutter analyze clean, all 161 tests green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

android/app/google-services.json

@@ -0,0 +1,29 @@
+{
+  "project_info": {
+    "project_number": "190209969950",
+    "project_id": "block-seasons",
+    "storage_bucket": "block-seasons.firebasestorage.app"
+  },
+  "client": [
+    {
+      "client_info": {
+        "mobilesdk_app_id": "1:190209969950:android:e08dc30877b1821b44c30f",
+        "android_client_info": {
+          "package_name": "com.airkjw.blockseasons"
+        }
+      },
+      "oauth_client": [],
+      "api_key": [
+        {
+          "current_key": "AIzaSyCd_3Tw5IxlO6ysp3XMQ9tBsOM1yMYl2MU"
+        }
+      ],
+      "services": {
+        "appinvite_service": {
+          "other_platform_oauth_client": []
+        }
+      }
+    }
+  ],
+  "configuration_version": "1"
+}