chore: httpx retry transport + healthcheck stdlib + mypy config

- mcp_common/http.py: nuovo helper async_client() con
  AsyncHTTPTransport(retries=3) per gestire connection error transient
  + call_with_retry() generic async retry decorator. Sostituite 25
  occorrenze httpx.AsyncClient(...) in deribit/hyperliquid/sentiment/
  macro client. 5 nuovi test.

- Dockerfile healthcheck: passato da python+httpx subprocess a
  stdlib urllib.request.urlopen() su tutti i 6 servizi MCP. Zero
  dipendenze esterne nel runtime check, timeout esplicito 3s, image
  leggermente più snella.

- pyproject.toml: aggiunto [tool.mypy] python_version=3.13 con
  mypy_path multi-package + override ignore_missing_imports per i
  vendor SDK (pybit, alpaca, hyperliquid, pythonjsonlogger). mypy 1.20
  in dev deps; ruff pinned 0.5.x. mcp_common passa mypy clean; 44
  errori tipo pre-esistenti nei servizi affiorati ma non bloccanti —
  fix da pianificare separatamente.

- 455 test verdi.

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

services/common/src/mcp_common/server.py

@@ -7,6 +7,7 @@ import uuid
 from collections.abc import Callable
 from contextlib import AbstractAsyncContextManager
 from datetime import UTC, datetime
+from typing import Any
 
 from fastapi import FastAPI, HTTPException, Request
 from fastapi.exceptions import RequestValidationError
@@ -28,7 +29,7 @@ def _error_envelope(
     details: dict | None = None,
     request_id: str | None = None,
 ) -> dict:
-    env = {
+    env: dict[str, Any] = {
         "error": {
             "type": type_,
             "code": code,