feat(confidence-engine): establish authenticated product boundary

app/api/focused-investigation/formulate/route.js

@@ -1,6 +1,7 @@
 import { formulateQuestionForTarget } from "@/lib/graph/focused-investigation";
+import { withAuthenticatedApi } from "@/lib/supabase/api-auth.js";
 
-export async function POST(request) {
+async function post(request) {
   try {
     const body = await request.json();
 
@@ -50,3 +51,5 @@ export async function POST(request) {
     );
   }
 }
+
+export const POST = withAuthenticatedApi(post);