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/http.py

@@ -0,0 +1,85 @@
+"""HTTP client factory con retry/backoff su errori transient.
+
+Wrap leggero attorno a httpx.AsyncClient: aggiunge AsyncHTTPTransport
+con retries=N per gestire connection errors / DNS / refused. Per retry
+su 5xx HTTP response usa `request_with_retry()` (decoratore separato).
+
+Usage standard:
+
+    async with async_client(timeout=15) as http:
+        resp = await http.get(url)
+
+Equivalente a httpx.AsyncClient(timeout=15) ma con retry transport su
+errori di livello connessione.
+"""
+from __future__ import annotations
+
+import asyncio
+import logging
+from collections.abc import Awaitable, Callable
+from typing import Any, TypeVar
+
+import httpx
+
+logger = logging.getLogger(__name__)
+
+T = TypeVar("T")
+
+DEFAULT_RETRIES = 3
+DEFAULT_TIMEOUT = 15.0
+
+
+def async_client(
+    *,
+    timeout: float = DEFAULT_TIMEOUT,
+    retries: int = DEFAULT_RETRIES,
+    follow_redirects: bool = False,
+    **kwargs: Any,
+) -> httpx.AsyncClient:
+    """httpx.AsyncClient con AsyncHTTPTransport(retries=N) di default.
+    retries gestisce connection errors / refused / DNS — non 5xx HTTP.
+    """
+    transport = httpx.AsyncHTTPTransport(retries=retries)
+    return httpx.AsyncClient(
+        timeout=timeout,
+        transport=transport,
+        follow_redirects=follow_redirects,
+        **kwargs,
+    )
+
+
+async def call_with_retry(
+    fn: Callable[[], Awaitable[T]],
+    *,
+    max_attempts: int = 3,
+    base_delay: float = 0.5,
+    max_delay: float = 8.0,
+    retry_on: tuple[type[BaseException], ...] = (httpx.TransportError, httpx.TimeoutException),
+) -> T:
+    """Retry generico async con exponential backoff.
+
+    Ritenta `fn()` se solleva una delle exception in `retry_on`. Backoff
+    raddoppia (0.5, 1, 2, 4, ...) clipped a max_delay. Solleva l'ultima
+    exception se max_attempts raggiunto.
+
+    Usabile su SDK sincroni avvolti in asyncio.to_thread (pybit, alpaca):
+
+        result = await call_with_retry(lambda: client._run(self._http.get_tickers, ...))
+    """
+    delay = base_delay
+    last_exc: BaseException | None = None
+    for attempt in range(1, max_attempts + 1):
+        try:
+            return await fn()
+        except retry_on as e:
+            last_exc = e
+            if attempt == max_attempts:
+                break
+            logger.warning(
+                "transient error, retrying (%d/%d) in %.1fs: %s",
+                attempt, max_attempts, delay, type(e).__name__,
+            )
+            await asyncio.sleep(delay)
+            delay = min(delay * 2, max_delay)
+    assert last_exc is not None
+    raise last_exc

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,

services/common/tests/test_http.py

@@ -0,0 +1,73 @@
+from __future__ import annotations
+
+import asyncio
+
+import httpx
+import pytest
+
+from mcp_common.http import async_client, call_with_retry
+
+
+def test_async_client_uses_retry_transport():
+    c = async_client(retries=5)
+    assert isinstance(c._transport, httpx.AsyncHTTPTransport)
+    # internal _retries on transport
+    assert c._transport._pool._retries == 5
+
+
+@pytest.mark.asyncio
+async def test_call_with_retry_succeeds_first_try():
+    calls = 0
+
+    async def fn():
+        nonlocal calls
+        calls += 1
+        return "ok"
+
+    result = await call_with_retry(fn)
+    assert result == "ok"
+    assert calls == 1
+
+
+@pytest.mark.asyncio
+async def test_call_with_retry_recovers_after_transient(monkeypatch):
+    monkeypatch.setattr(asyncio, "sleep", asyncio.coroutine(lambda *_: None) if False else _no_sleep)
+    calls = 0
+
+    async def fn():
+        nonlocal calls
+        calls += 1
+        if calls < 3:
+            raise httpx.ConnectError("boom")
+        return "ok"
+
+    result = await call_with_retry(fn, max_attempts=5, base_delay=0.0)
+    assert result == "ok"
+    assert calls == 3
+
+
+async def _no_sleep(_):
+    return None
+
+
+@pytest.mark.asyncio
+async def test_call_with_retry_gives_up_after_max():
+    calls = 0
+
+    async def fn():
+        nonlocal calls
+        calls += 1
+        raise httpx.TimeoutException("slow")
+
+    with pytest.raises(httpx.TimeoutException):
+        await call_with_retry(fn, max_attempts=3, base_delay=0.0)
+    assert calls == 3
+
+
+@pytest.mark.asyncio
+async def test_call_with_retry_does_not_catch_unexpected():
+    async def fn():
+        raise ValueError("not transient")
+
+    with pytest.raises(ValueError):
+        await call_with_retry(fn, max_attempts=5, base_delay=0.0)