Role-based access: admin vs superadmin

- Credentials provider now resolves two distinct accounts from env:
    SUPERADMIN_USERNAME / SUPERADMIN_PASSWORD → role "superadmin"
    ADMIN_USERNAME      / ADMIN_PASSWORD      → role "admin"
  The role is carried through the JWT and Session callbacks so the UI
  and API can gate on it. Types extended via types/next-auth.d.ts.
- lib/auth.ts exports requireRole(minRole) and sessionRole(session).
- /api/players POST rejects "op" and "deop" with 403 unless the caller
  is superadmin. All other player actions (whitelist add/remove, ban,
  pardon) remain available to both roles.
- lib/use-role.ts (client hook) exposes role / isSuperadmin / authed
  for UI gating without duplicating session typing.
- PlayerManager: Add-OP button and per-row Deop action are hidden or
  disabled for non-superadmin; when a regular admin is viewing the
  Ops tab, a banner explains the read-only state.
- PlayerDrawer: Make Op / Deop button disabled with tooltip for
  non-superadmin; whitelist, ban, pardon unchanged.
- Navbar: subtle role pill next to the user name ("Super" for
  superadmin amber-tinted, "Admin" for admin).
- Migration note: the existing ADMIN_* credentials now log in as the
  restricted admin role. Set SUPERADMIN_USERNAME + SUPERADMIN_PASSWORD
  in .env.local to retain operator-management ability. A placeholder
  superadmin account was generated in .env.local; the password is in
  the commit terminal output only, not the repo.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

components/Navbar.tsx

@@ -7,6 +7,7 @@ import { ThemeToggle } from "@/components/ThemeToggle";
 
 export function Navbar() {
   const { data: session } = useSession();
+  const role = (session?.user as { role?: "admin" | "superadmin" } | undefined)?.role;
 
   return (
     <header className="border-b border-border bg-card">
@@ -24,6 +25,18 @@ export function Navbar() {
           <ThemeToggle />
           {session ? (
             <>
+              {role && (
+                <span
+                  className={`hidden sm:inline-flex items-center rounded-full px-2 py-0.5 text-[10px] font-semibold uppercase tracking-wide border ${
+                    role === "superadmin"
+                      ? "border-amber-500/40 bg-amber-500/10 text-amber-300"
+                      : "border-border bg-muted text-muted-foreground"
+                  }`}
+                  title={`Signed in as ${session.user?.name} (${role})`}
+                >
+                  {role === "superadmin" ? "Super" : "Admin"}
+                </span>
+              )}
               <Button variant="ghost" size="sm" render={<Link href="/admin" />}>
                 Admin
               </Button>