Admin Persona Backfill

2026-05-19 — sweep activities with a non-empty lineup JSON column, materialise activity_lineup rows for every name, and resolve each to an entity (creating placeholder shells for unmatched names).

This handles the case where activities exist (imported / created before today's persona pipeline) but no one has visited them yet, so the opportunistic resolver in /api/lineup/:id hasn't fired.

Admin-gated — only users with is_admin=true may run it. Idempotent: re-running is safe (skips lineup rows that already exist).

Returns: { "scanned": number of activities inspected, "materialised_rows": number of activity_lineup rows inserted, "resolved_entities": number of unique entity matches/creations, "placeholders_created": number of new placeholder entities, }