fix: filter hardcoded FastAPI params from **extra to prevent TypeError

[hieusats]

Problem

Passing , , , , , , or through raises a confusing TypeError: FastAPI.__init__() got multiple values for keyword argument.

These params were user-settable when Air inherited from FastAPI. The composition refactor hardcoded them to None but still forwards **extra to FastAPI(), causing the conflict.

import air
app = air.Air(docs_url="/docs")  # TypeError!

Fix

Filter the 7 reserved params from **extra before forwarding to FastAPI(). This prevents the conflict while keeping the hardcoded None values intact (Air manages these internally).

Closes #1073