docs(templates): document CRUD and model CRUD apps and expose them in mkdocs

- Add comprehensive module and function docstrings to crud_app and model_app templates
- Document OpenAPI-first guarantees, non-goals, and usage patterns in templates
- Add template-level __init__.py files with CLI and client usage examples
- Update mkdocs.yml to include CRUD and model-based CRUD template documentation
- Ensure template documentation follows strict package-bound mkdocstrings rules

openapi_first/templates/model_app/test_model_app.py

@@ -3,6 +3,13 @@ End-to-end tests for the OpenAPI-first model CRUD example app.
 
 These tests validate that all CRUD operations behave correctly
 against the in-memory mock data store using Pydantic models.
+- OpenAPI specification loading
+- OperationId-driven route binding on the server
+- OperationId-driven client invocation
+- Pydantic model-based request and response handling
+
+All CRUD operations are exercised against an in-memory mock data store
+backed by Pydantic domain models.
 
 The tests assume:
 - OpenAPI-first route binding