ASN name and first-seen IP enrichment

The stream processing pipeline now writes richer network attribution onto every view.

1. Added the asnName dimension so you can break down playback by autonomous-system / ISP name, not just numeric ASN.
2. The IP address recorded on a view is now pinned to the first occurrence within the session rather than being overwritten by later beacons, giving a stable join key for fraud and geo analysis.
3. Both fields flow through to filters and breakdowns in the Data APIs.