feat(data): mirror ETH spot+DVOL in dvol_history dal market_snapshot

Popola dvol_history dentro la stessa transazione di market_snapshots,
così lo storico è disponibile anche in modalità data-only (STRATEGY=false).
Evita il warm-up vuoto di return_4h quando si abilita la strategia: il
monitor_cycle trova subito i campioni locali invece di dipendere dal
fallback Deribit get_historical.

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

src/cerbero_bite/runtime/market_snapshot_cycle.py

@@ -22,7 +22,7 @@ from typing import TYPE_CHECKING, Any
 
 from cerbero_bite.clients._exceptions import McpError
 from cerbero_bite.state import connect, transaction
-from cerbero_bite.state.models import MarketSnapshotRecord
+from cerbero_bite.state.models import DvolSnapshot, MarketSnapshotRecord
 
 if TYPE_CHECKING:
     from cerbero_bite.runtime.dependencies import RuntimeContext
@@ -181,6 +181,21 @@ async def collect_market_snapshot(
             try:
                 with transaction(conn):
                     ctx.repository.record_market_snapshot(conn, record)
+                    # Mirror ETH spot+DVOL into dvol_history so monitor_cycle's
+                    # return_4h lookup has local samples even in data-only mode.
+                    if (
+                        record.asset == "ETH"
+                        and record.spot is not None
+                        and record.dvol is not None
+                    ):
+                        ctx.repository.record_dvol_snapshot(
+                            conn,
+                            DvolSnapshot(
+                                timestamp=record.timestamp,
+                                dvol=record.dvol,
+                                eth_spot=record.spot,
+                            ),
+                        )
             finally:
                 conn.close()
             persisted += 1