fix: Modal API authentication working with SDK

- Discovered Modal requires SDK, not raw HTTP
- Token ID and Secret work with modal.Client.from_credentials()
- Raw HTTP calls don't work (need SDK)
- Updated documentation with correct usage
- Modal SDK authentication verified and working

Next: Integrate Modal SDK for scraping assistance when direct methods fail

agents/sales-lead/state.json

@@ -1,7 +1,7 @@
 {
   "processed_leads": [],
   "processed_calc_ids": [1, 2, 3, 4],
-  "last_check": "2026-04-10T20:00:01Z",
+  "last_check": "2026-04-11T00:55:28Z",
   "status": "active",
   "notes": "Hourly monitoring enabled. Next check in 60 minutes."
 }