feat(runtime): orchestrator option-chain snapshot multi-asset (ETH+BTC)

Sostituisce `option_chain_asset: str = "ETH"` con
`option_chain_assets: tuple[str, ...] = ("ETH", "BTC")` e itera nel
job schedulato. Coerente con `market_snapshot_assets` già multi-asset
e con i 64 strikes BTC + 51 strikes ETH già visibili in
option_chain_snapshots.

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

src/cerbero_bite/runtime/orchestrator.py

@@ -222,7 +222,7 @@ class Orchestrator:
         market_snapshot_cron: str = _CRON_MARKET_SNAPSHOT,
         market_snapshot_assets: tuple[str, ...] = DEFAULT_ASSETS,
         option_chain_cron: str = _CRON_OPTION_CHAIN_SNAPSHOT,
-        option_chain_asset: str = "ETH",
+        option_chain_assets: tuple[str, ...] = ("ETH", "BTC"),
         backup_dir: Path | None = None,
         backup_retention_days: int = _BACKUP_RETENTION_DAYS,
     ) -> AsyncIOScheduler:
@@ -290,9 +290,8 @@ class Orchestrator:
 
         async def _option_chain_snapshot() -> None:
             async def _do() -> None:
-                await collect_option_chain_snapshot(
-                    self._ctx, asset=option_chain_asset
-                )
+                for asset in option_chain_assets:
+                    await collect_option_chain_snapshot(self._ctx, asset=asset)
 
             await _safe("option_chain_snapshot", _do)