Add neutral administrator lobby configuration

Configure supported rules/modules and AI seats or assign an existing human as host without granting private-seat access. Use genuine unused-lobby checks, existing engine actions, live authorization/version/pause/seat fences and atomic audit receipts. Preserve exact account-bound retries across refresh and confirm completed operations after game start without resetting play.

Verified types, lint, 5260 offline tests, 52 HTTP tests and build. Eleven authenticated HTTP groups and independent privacy/persistence review passed. Browser QA confirmed one AI and audit after a lost response and refresh/retry, persisted rules and AI configuration, and readable 1280/390px layouts. All existing rooms and seats preserved. Actual authenticated production administrator acceptance remains pending authorized QA operator access.

app/api/admin/rooms/[code]/lobby/route.ts

@@ -0,0 +1,31 @@
+import { env } from 'cloudflare:workers';
+import { AdminError, requireAdmin } from '@/db/admin-access';
+import { configureAdminLobby, readAdminLobby } from '@/db/admin-lobby-configuration';
+import { validAdminLobbyInput } from '@/lib/admin-lobby-configuration';
+import { adminBody, adminFailure, adminResponse, adminToken } from '@/lib/admin-http';
+
+function code(request: Request) {
+  const code = new URL(request.url).pathname.split('/').at(-2)?.toUpperCase() ?? '';
+  if (code.length !== 8 || !/^[A-Z2-9]{8}$/.test(code)) throw new AdminError('Enter the eight-character room code.', 400);
+  return code;
+}
+
+export async function GET(request: Request) {
+  try {
+    const identity = await requireAdmin(env.DB, adminToken(request));
+    if (request.headers.has('X-Dune-Admin-Id') && request.headers.get('X-Dune-Admin-Id') !== identity.id)
+      throw new AdminError('The signed-in administrator changed. Reload administration before continuing.', 401);
+    return adminResponse(await readAdminLobby(env.DB, identity, code(request)));
+  } catch (error) { return adminFailure(error); }
+}
+
+export async function POST(request: Request) {
+  try {
+    const body = await adminBody(request, env.DUNE_PUBLIC_ORIGIN);
+    const identity = await requireAdmin(env.DB, adminToken(request), ['owner', 'operator']);
+    if (request.headers.get('X-Dune-Admin-Id') !== identity.id)
+      throw new AdminError('The signed-in administrator changed. Reload administration before continuing.', 401);
+    if (!validAdminLobbyInput(body)) throw new AdminError('Choose a lobby change, revision and operational reason.', 400);
+    return adminResponse(await configureAdminLobby(env.DB, identity, code(request), body));
+  } catch (error) { return adminFailure(error); }
+}