[Admin Console] Phase 6: Payments and Admissions View #636

Operators running paid relays have no dashboard to see revenue, invoice status, or admission history. Checking payment processor health requires reading logs or querying the database directly.

• Total admission fees recorded
• List of pending, paid, expired, and failed invoices
• Recent admissions by pubkey
• Payment processor health check
• Callback failure history
• Manual invoice lookup by id
• Admission whitelist management