fix: Improved duplicate prevention in cast iron scanner

- Better link normalization and checking
- Skip items already in seen_links with logging
- Clean up state file to last 500 items
- Always mark items as seen (deal or not)
- Added logging for skipped duplicates

Also: eBay scraping temporarily blocked/changed - investigating

.clawhub/lock.json

@@ -44,6 +44,10 @@
     "deep-scraper": {
       "version": "1.0.1",
       "installedAt": 1775821381724
+    },
+    "marketplace": {
+      "version": "1.0.1",
+      "installedAt": 1775850557338
     }
   }
 }