chore: ruff py313, conftest unification, audit log, app factory comune

- pyproject.toml: ruff target-version py311 → py313 (auto-fix 42 lint
  warnings via UP rules); aggiunto consider_namespace_packages = true
  che risolve la collisione conftest tra servizi e permette di lanciare
  pytest sull'intera suite cross-servizio.

- mcp_common.audit: nuovo helper audit_write_op() con logger dedicato
  mcp.audit. Wirato su tutti i write endpoint di deribit, bybit, alpaca
  e hyperliquid (place_order, place_combo_order, cancel_*, set_*,
  close_*, transfer_*, switch_*, amend_*) con principal + target +
  payload non-sensibile + result summarizzato.

- mcp_common.app_factory: ExchangeAppSpec + run_exchange_main()
  centralizza il boilerplate dei __main__.py (configure_root_logging,
  fail_fast_if_missing, summarize, load creds, resolve_environment,
  load token store, uvicorn). I 4 __main__.py exchange ridotti da ~60
  LOC ognuno a ~25 LOC dichiarativi. mcp_common.env_validation
  promosso da mcp_deribit (mantenuto re-export shim per back-compat
  test_env_validation).

- 8 test nuovi (4 audit + 4 app_factory). Suite full: 450/450 verdi.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

services/common/src/mcp_common/server.py

@@ -4,10 +4,9 @@ import json
 import os
 import time
 import uuid
-from datetime import UTC, datetime
-
 from collections.abc import Callable
 from contextlib import AbstractAsyncContextManager
+from datetime import UTC, datetime
 
 from fastapi import FastAPI, HTTPException, Request
 from fastapi.exceptions import RequestValidationError