feat: basic admin interface

server/api/instance.get.ts

@@ -0,0 +1,6 @@
+// Public on purpose: the sign in pages ask this before anyone is signed in.
+export default defineEventHandler(async () => {
+    const [setupNeeded, registration] = await Promise.all([isSetupNeeded(), getRegistrationMode()]);
+
+    return { setupNeeded, registration };
+});