Muse → Settings → Redeem token · Web: Settings → General → Usage → Redeem invite code
POST /api/codes { "code": "ABC123", "contact": "optional" }
GET /api/codes/claim → { "code": "ABC123" }
POST /api/codes/report { "code": "ABC123", "result": "worked" | "used_up" }
POST /api/fillup { "code": "ABC123", "contact": "how to reach you" }