chore: convert submodules to standard directories for true monorepo structure

vibn-frontend/app/api/sentry-example-api/route.ts

@@ -0,0 +1,21 @@
+/**
+ * Companion endpoint to /sentry-example-page. Throws on every call
+ * so the "Throw server error" button has something real to fail
+ * against. The thrown error propagates to instrumentation.ts'
+ * onRequestError hook and lands in Sentry as a server-side issue.
+ */
+
+export const dynamic = "force-dynamic";
+
+class SentryExampleApiError extends Error {
+  constructor(message: string) {
+    super(message);
+    this.name = "SentryExampleApiError";
+  }
+}
+
+export function GET() {
+  throw new SentryExampleApiError(
+    "Sentry test (API route) — vibn-ai",
+  );
+}