feat(V2): /health/ready con ping client + middleware request log strutturato + request_id correlation

- /health/ready: ping di tutti i client (exchange, env) cached con
  timeout 2s, status ready|degraded|not_ready, opt-in 503 via
  READY_FAILS_ON_DEGRADED.
- Middleware mcp.request: 1 riga JSON per HTTP request con request_id,
  method, path, status_code, duration_ms, actor, bot_tag, exchange,
  tool, client_ip, user_agent.
- request_id propagato in request.state, audit log e error envelope per
  correlazione cross-cutting.
- Aggiunto async health() come probe minimo a bybit/alpaca/macro/
  sentiment/deribit (hyperliquid lo aveva già).

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

src/cerbero_mcp/common/audit.py

@@ -74,6 +74,7 @@ def audit_write_op(
     payload: dict[str, Any] | None = None,
     result: dict[str, Any] | None = None,
     error: str | None = None,
+    request_id: str | None = None,
 ) -> None:
     """Emit a structured audit log record per write operation.
 
@@ -86,6 +87,8 @@ def audit_write_op(
     payload: input non-sensibile (qty, side, leverage, ecc.).
     result: output del client (order_id, status, ecc.).
     error: stringa errore se l'operazione ha fallito.
+    request_id: id propagato dal middleware request log per correlazione
+        tra audit log e request log.
     """
     _configure_audit_sink()
     record: dict[str, Any] = {
@@ -97,6 +100,8 @@ def audit_write_op(
         "target": target,
         "payload": payload or {},
     }
+    if request_id is not None:
+        record["request_id"] = request_id
     if result is not None:
         record["result"] = _summarize_result(result)
     if error is not None: