Initialize project and update portal port configuration

Set default portal port to 8081, fix Dart build issue in cart screen, and update setup documentation.

Co-Authored-By: Oz <oz-agent@warp.dev>

assets/config/runtime_config.json

@@ -0,0 +1,9 @@
+{
+  "firebase_api_key": "replace-with-firebase-api-key",
+  "firebase_auth_domain": "replace-with-project-id.firebaseapp.com",
+  "firebase_project_id": "replace-with-project-id",
+  "firebase_storage_bucket": "replace-with-project-id.appspot.com",
+  "firebase_messaging_sender_id": "replace-with-sender-id",
+  "firebase_app_id": "replace-with-app-id",
+  "firebase_measurement_id": ""
+}