Hardening round 2: healthcheck, audit anchor, return_4h, exec config, signals

Sei interventi MEDIA priorità sul sistema. 323 test pass, mypy strict
pulito, ruff clean.

1. Docker HEALTHCHECK + cerbero-bite healthcheck:
   - nuovo subcommand che esce 0 se kill_switch=0 e last_health_check
     entro --max-staleness-s (default 600s);
   - HEALTHCHECK direttiva nel Dockerfile (60s interval, 5s timeout,
     start_period 120s, retries 3);
   - healthcheck definition nel docker-compose.yml.

2. Audit hash chain anti-truncation:
   - migration 0002: nuova colonna system_state.last_audit_hash;
   - AuditLog accetta callback on_append, dependencies.py la wire al
     repository.set_last_audit_hash;
   - Orchestrator.boot verifica che il tail file matcha l'anchor
     persistito; mismatch → kill switch CRITICAL.

3. return_4h bootstrap da deribit get_historical:
   - quando dvol_history è vuoto _fetch_return_4h cade su
     deribit.historical_close (1h candle 4h fa);
   - alert LOW se anche il fallback fallisce.

4. execution.environment + execution.eur_to_usd in strategy.yaml:
   - ExecutionConfig promosso a typed schema con i due campi
     consumati al boot;
   - CLI start preferisce i valori da config; CLI flag overridano
     solo quando differenti dai default.

5. Cycle correlation ID:
   - structlog.contextvars.bind_contextvars in run_entry/run_monitor/
     run_health propaga cycle_id e cycle nei log strutturati.

6. SIGTERM/SIGINT clean shutdown:
   - run_forever installa loop.add_signal_handler per SIGTERM e
     SIGINT; il segnale set()ta un asyncio.Event che termina il
     blocco principale, scheduler.shutdown e ctx.aclose finalizzano.

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

tests/integration/test_monitor_cycle.py

@@ -98,6 +98,7 @@ def _wire_market_data(
     *,
     spot: float = 3000.0,
     dvol: float = 50.0,
+    historical_close: float | None = None,
 ) -> None:
     httpx_mock.add_response(
         url="http://mcp-deribit:9011/tools/get_ticker",
@@ -109,6 +110,16 @@ def _wire_market_data(
         json={"currency": "ETH", "latest": dvol, "candles": []},
         is_reusable=True,
     )
+    # Bootstrap fallback for return_4h when dvol_history is empty.
+    httpx_mock.add_response(
+        url="http://mcp-deribit:9011/tools/get_historical",
+        json={
+            "candles": (
+                [{"close": historical_close}] if historical_close is not None else []
+            )
+        },
+        is_reusable=True,
+    )
 
 
 def _wire_position_quotes(