Align /_ts/admin/eids preview with EID ingestion (consent gate and /auction body) #1232

Follow-up from #1188.

handle_admin_eids_lookup (crates/trusted-server-core/src/ec/admin.rs) previews partner-ID matches from the ts-eids and sharedId cookies only. After #1188, response-finalization ingestion differs in two ways the preview does not reflect:

• Identity-graph EID writes require TCF Purpose 1 + 4 (allows_eid_persistence), so for a Purpose-4-denied request the preview lists matches that are never written.
• POST /auction also ingests request-body EIDs, which the GET preview cannot see.

It also ignores add-only semantics from #1157 (a different stored UID is kept).

#1188 documents the preview as cookie-only and ungated. Options:

1. Run the preview through allows_eid_persistence (building consent from the request) and report a consent_gated flag.
2. Keep it cookie-only and expose the consent decision as a separate field.

Raised in review of #1188.