Add admin foundation + Users resource (Filament replacement, slice 1)
Plain App Router admin (aligned to habbo-next, no Refine):
- rank surfaced on the NextAuth session; staff guard isStaff() [pure,
unit-tested] + requireStaff() reading min_staff_rank, gating /admin.
- /admin dashboard (counts), /admin/users (paginated + search),
/admin/users/[id] detail.
- src/actions/admin-users.ts: staff-gated server actions wiring the user editor
to the existing services — giveCurrency (RCON or DB fallback), setMotto/setRank
(DB + RCON), alertUser, disconnectUser.
Verified: tsc exit 0, vitest 45/45, next build exit 0 (/admin routes).
Simo
9f81096f05