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>

docker/mcp-deribit.Dockerfile

@@ -21,6 +21,6 @@ ENV HOST=0.0.0.0 PORT=9011
 EXPOSE 9011
 
 HEALTHCHECK --interval=30s --timeout=5s --retries=3 --start-period=15s \
-    CMD python -c "import httpx, os; httpx.get(f'http://localhost:{os.environ.get(\"PORT\",\"9011\")}/health').raise_for_status()"
+    CMD python -c "import os, urllib.request; urllib.request.urlopen(f'http://localhost:{os.environ.get(\"PORT\",\"9011\")}/health', timeout=3).close()"
 
 CMD ["mcp-deribit"]