fix(server): annotate unused on_starting parameter as _server: Any (#2)

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: nanotaboada

gunicorn.conf.py

@@ -9,6 +9,7 @@
 import multiprocessing
 import os
 from pathlib import Path
+from typing import Any
 
 from alembic import command
 from alembic.config import Config
@@ -18,7 +19,7 @@
 worker_class: str = "uvicorn.workers.UvicornWorker"
 
 
-def on_starting(server) -> None:
+def on_starting(_server: Any) -> None:
     """Apply Alembic migrations once before workers are spawned."""
     alembic_cfg = Config(str(Path(__file__).resolve().parent / "alembic.ini"))
     command.upgrade(alembic_cfg, "head")