/admin dashboard + Clerk magic-link auth

[quinn-dougherty]

Description

Protected admin + curator review surface. PLAYBOOK.md §1, §6, §7.

Auth

• Clerk via Vercel Marketplace (faster than rolling custom magic links).
• Admin gated by email allowlist env var (`ADMIN_EMAILS`).
• Curators authenticated via magic link to their application email.

Views

• `/admin` — registrant list, Discord invite status, reconciliation queue.
• `/admin/curator-apps` — queue with accept/reject; accept promotes to `curators`.
• `/admin/review` (curator-visible) — submissions on their track(s) with score (1–5) + comment.
• Auto-decide: submission → `decided` when ≥2 reviews and average ≥ 3.5 (configurable). Quinn breaks ties.
• `/admin/decisions` — batch-send decision emails, not per-submission.

Dependencies

• Data model (new infra issue).
• Email (new email issue).