feat(state): Repository.iv_rv_history + dvol_lookback per gate adaptive

Due nuovi metodi che leggono market_snapshots filtrando NULL e
fetch_ok=0. iv_rv_history limita a max_days; dvol_lookback trova
il tick più vicino a un istante con tolerance configurabile.

Tests: ordered ASC, asset filter, NULL skip, fetch_ok=0 skip,
lookback closest, gap returns None.

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

src/cerbero_bite/state/repository.py

@@ -13,7 +13,7 @@ Decimals are stored as TEXT to preserve precision (see
 from __future__ import annotations
 
 import sqlite3
-from datetime import UTC, datetime
+from datetime import UTC, datetime, timedelta
 from decimal import Decimal
 from typing import Any
 from uuid import UUID
@@ -408,6 +408,64 @@ class Repository:
         ).fetchall()
         return [_row_to_market_snapshot(r) for r in rows]
 
+    def iv_rv_history(
+        self,
+        conn: sqlite3.Connection,
+        *,
+        asset: str,
+        max_days: int,
+    ) -> list[Decimal]:
+        """Lista IV-RV ordinata ASC sull'intervallo `[now-max_days, now]`.
+
+        Esclude righe con ``fetch_ok=0`` o ``iv_minus_rv IS NULL``.
+        Usata dal validator quando il gate adattivo è abilitato.
+        """
+        rows = conn.execute(
+            "SELECT iv_minus_rv FROM market_snapshots "
+            "WHERE asset = ? "
+            "  AND fetch_ok = 1 "
+            "  AND iv_minus_rv IS NOT NULL "
+            "  AND timestamp >= datetime('now', ?) "
+            "ORDER BY timestamp ASC",
+            (asset, f"-{int(max_days)} days"),
+        ).fetchall()
+        return [Decimal(str(r["iv_minus_rv"])) for r in rows]
+
+    def dvol_lookback(
+        self,
+        conn: sqlite3.Connection,
+        *,
+        asset: str,
+        reference: datetime,
+        tolerance_minutes: int = 15,
+    ) -> Decimal | None:
+        """DVOL al tick più vicino a `reference`, entro ±tolerance_minutes.
+
+        Ritorna ``None`` se non esiste un tick valido (``fetch_ok=1``,
+        ``dvol IS NOT NULL``) entro la tolerance. Usato dal Vol-of-Vol
+        guard per stimare DVOL N ore fa.
+        """
+        ref_lo = (reference - timedelta(minutes=tolerance_minutes)).astimezone(UTC)
+        ref_hi = (reference + timedelta(minutes=tolerance_minutes)).astimezone(UTC)
+        row = conn.execute(
+            "SELECT dvol, timestamp FROM market_snapshots "
+            "WHERE asset = ? "
+            "  AND fetch_ok = 1 "
+            "  AND dvol IS NOT NULL "
+            "  AND timestamp >= ? "
+            "  AND timestamp <= ? "
+            "ORDER BY ABS(julianday(timestamp) - julianday(?)) ASC LIMIT 1",
+            (
+                asset,
+                _enc_dt(ref_lo),
+                _enc_dt(ref_hi),
+                _enc_dt(reference),
+            ),
+        ).fetchone()
+        if row is None:
+            return None
+        return Decimal(str(row["dvol"]))
+
     # ------------------------------------------------------------------
     # option_chain_snapshots
     # ------------------------------------------------------------------