fix: invalidate IV watchlist cache after cycle fetches fresh IV data

The auto-cycle was saving new IV snapshots to SQLite but not clearing
the in-memory cache in options_vol.py (TTL 1h), so the Options Lab
page kept showing stale IV Rank data until the cache naturally expired.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/services/auto_cycle.py

@@ -348,6 +348,16 @@ def run_cycle_once(trigger: str = "auto") -> Dict[str, Any]:
             iv_context = get_iv_context_for_prompt(_iv_tickers)
             if iv_context:
                 logger.info(f"[Cycle {run_id[:16]}] IV context collected for {len(_iv_tickers)} tickers")
+            # Invalidate the options_vol watchlist cache so the frontend sees fresh data
+            try:
+                from routers.options_vol import _iv_cache
+                stale_keys = [k for k in list(_iv_cache.keys()) if k.startswith("watchlist:") or k.startswith("snapshot:")]
+                for k in stale_keys:
+                    _iv_cache.pop(k, None)
+                if stale_keys:
+                    logger.info(f"[Cycle] IV cache invalidated ({len(stale_keys)} entries)")
+            except Exception:
+                pass
         except Exception as _e:
             logger.warning(f"[Cycle] IV context collection failed (non-blocking): {_e}")