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/exchanges/sentiment/client.py

@@ -9,6 +9,8 @@ e per essere istanziato dal `ClientRegistry`.
 """
 from __future__ import annotations
 
+from typing import Any
+
 
 class SentimentClient:
     """Wrapper credenziali CryptoPanic/LunarCrush. Stateless, no HTTP session."""
@@ -19,3 +21,7 @@ class SentimentClient:
 
     async def aclose(self) -> None:  # pragma: no cover - no-op, no resources
         return None
+
+    async def health(self) -> dict[str, Any]:
+        """Probe minimo per /health/ready: nessuna chiamata di rete."""
+        return {"status": "ok"}