Add authenticated login and SSO protection

app/api/prompt/assemble/route.ts

@@ -1,10 +1,12 @@
 import { assemblePrompt, type PromptAssemblyInput } from "@/lib/prompt/assembler";
 import { jsonError, jsonOk, readJsonBody } from "@/lib/server/api";
+import { requireAppUser } from "@/lib/server/auth/current-user";
 
 export const runtime = "nodejs";
 
 export async function POST(request: Request) {
   try {
+    await requireAppUser();
     const body = await readJsonBody<PromptAssemblyInput & Record<string, unknown>>(request);
     return jsonOk(assemblePrompt(body));
   } catch (error) {