Update admin theme/layout and refresh README details.

Align the project baseline with the latest admin interface styling and layout structure while documenting setup and usage updates in README.

apps/api/app/modules/orders/service.py

@@ -0,0 +1,5 @@
+"""Orders module placeholder (request/booking mode without payment)."""
+
+
+def create_order_request(user_id: str, items: list[dict]) -> dict:
+    return {"id": "order-placeholder", "user_id": user_id, "items": items, "status": "submitted"}