feat(scaffold): add model-backed CRUD service template

Provides a complete OpenAPI-first CRUD example with a Pydantic
model layer, explicit runtime semantics, and integration tests
to support developer onboarding and real-world service structure.

openapi_first/templates/model_app/routes.py

@@ -0,0 +1,48 @@
+"""
+CRUD route handlers bound via OpenAPI operationId.
+"""
+
+from fastapi import Response, HTTPException
+
+from models import ItemCreate
+from data import (
+    list_items as _list_items,
+    get_item as _get_item,
+    create_item as _create_item,
+    update_item as _update_item,
+    delete_item as _delete_item,
+)
+
+
+def list_items():
+    return _list_items()
+
+
+def get_item(item_id: int):
+    try:
+        return _get_item(item_id)
+    except KeyError:
+        raise HTTPException(status_code=404, detail="Item not found")
+
+
+def create_item(payload: ItemCreate, response: Response):
+    item = _create_item(payload)
+    response.status_code = 201
+    return item
+
+
+def update_item(item_id: int, payload: ItemCreate):
+    try:
+        return _update_item(item_id, payload)
+    except KeyError:
+        raise HTTPException(status_code=404, detail="Item not found")
+
+
+def delete_item(item_id: int, response: Response):
+    try:
+        _delete_item(item_id)
+    except KeyError:
+        raise HTTPException(status_code=404, detail="Item not found")
+
+    response.status_code = 204
+    return None