feat: add admin REST API layer for frontend management panel
Implement JWT-protected /admin/* routes on the relay server:
- Auth: login, logout, me, setup/status, setup/init (first-time config)
- Dashboard: stats overview (connections, devices, cookies, domains)
- Cookies: paginated list with domain/search filter, detail, delete, batch delete
- Devices: list with online status, revoke
- Settings: get/update (sync interval, max devices, theme)
Uses scrypt for password hashing and jsonwebtoken for JWT.
Adds listAll/revoke to DeviceRegistry, getAll/getById/deleteById to CookieBlobStore,
disconnect to ConnectionManager. Updates frontend to use /admin/* endpoints.
All 38 existing tests pass.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
a320f7ad97