Add register + logout auth flows, and batch-5 resources

Auth (hand-built, uses the auth core):
- /register + register() action: validates, hashes with argon2id (hashPassword),
  creates an emulator-compatible users row (accountCreated/ipRegister/ipCurrent/
  look), redirect kept outside try so NEXT_REDIRECT propagates. Login/register
  cross-links; header shows Register (logged-out) and a Logout (signOut) button.

Batch 5 (parallel agents): /admin/rooms (+[id]) search+detail, /admin/vouchers
(CRUD), /admin/subscriptions (read), /admin/calendar (campaigns+rewards read),
/marketplace (public). Header + admin nav extended.

Verified: tsc exit 0, vitest 48/48, next build exit 0 (52 page routes).

src/app/admin/layout.tsx

@@ -16,11 +16,15 @@ export default async function AdminLayout({ children }: { children: ReactNode })
         <nav style={{ display: "grid", gap: "0.45rem" }}>
           <Link href="/admin">Dashboard</Link>
           <Link href="/admin/users">Users</Link>
+          <Link href="/admin/rooms">Rooms</Link>
           <Link href="/admin/articles">Articles</Link>
           <Link href="/admin/catalog">Catalog</Link>
+          <Link href="/admin/vouchers">Vouchers</Link>
           <Link href="/admin/badges">Badges</Link>
           <Link href="/admin/radio">Radio</Link>
           <Link href="/admin/achievements">Achievements</Link>
+          <Link href="/admin/subscriptions">Subscriptions</Link>
+          <Link href="/admin/calendar">Calendar</Link>
           <Link href="/admin/rare-values">Rare Values</Link>
           <Link href="/admin/photos">Photos</Link>
           <Link href="/admin/bans">Bans</Link>