backend(views): add response schemas for views

[r0liveir]

What to do:

Add responses for endpoints, an example:

@app.get("/user/{user_id}")
def get_user(user_id: int) -> UserOutput:

Or, legacy style:

@app.post("/users/", response_model=UserOutput)
def create_user(user_data: dict):

You may add schemas/models for this.

Expected behavior:
In docs endpoint, should preview the schema output

[r0liveir]

For websockets, we might need a custom openapi wrapper. An example from Gemini:

from fastapi.openapi.utils import get_openapi

def custom_openapi():
    if app.openapi_schema:
        return app.openapi_schema
    
    # Generate standard OpenAPI schema
    openapi_schema = get_openapi(
        title="My Custom API",
        version="1.0.0",
        routes=app.routes,
    )
    
    # Inject your WebSocket models manually into the OpenAPI components
    openapi_schema["components"]["schemas"]["ChatMessageIn"] = ChatMessageIn.model_json_schema()
    openapi_schema["components"]["schemas"]["ChatMessageOut"] = ChatMessageOut.model_json_schema()
    
    app.openapi_schema = openapi_schema
    return app.openapi_schema

app.openapi = custom_openapi