Feature: Add CMTS getSysDescr visual and collection wiring

- Create new visual for ServingGroup/CableModem/Operations/getSysDescr
- Add grouped Device Info tables by service group with modem metadata
- Add Summary PollType card and map value from poll.type fallback chain
- Remove unneeded summary cards and simplify device table columns
- Add Postman request for /cmts/servingGroup/cableModem/operations/getSysDescr
- Sync visual script into PyPNM-CMTS.postman_collection.json
- Regenerate visual docs/previews and keep docs/sync checks clean - 2026-03-03 23:26:41

Author: mgarcia01752