feat: Cast Iron Scout agent prototype

- Created autonomous cast iron deal scanner
- Scans eBay RSS feeds hourly for cast iron cookware
- Calculates FMV based on brand, type, size
- Sends Telegram alerts for deals ≥50% below FMV
- Identifies Griswold, Wagner, Wapak, Birmingham, Lodge, Victor
- Tracks seen items to avoid duplicate alerts
- Valuation engine with size multipliers
- Configurable preferences in config.json

Known issue: eBay RSS unreliable - next iteration will use proper scraping

agents/cast-iron-scout/state/seen_items.json

@@ -0,0 +1,4 @@
+{
+  "seen_links": [],
+  "last_scan": "2026-04-09T17:44:28.435221"
+}