chore: convert submodules to standard directories for true monorepo structure

vibn-frontend/app/api/debug/prisma/route.ts

@@ -0,0 +1,40 @@
+import { NextResponse } from "next/server";
+import { PrismaClient } from "@prisma/client";
+
+/**
+ * Dev-only: verifies Prisma can connect (NextAuth adapter needs this after Google redirects back).
+ * Open GET /api/debug/prisma while running next dev.
+ */
+export async function GET() {
+  if (process.env.NODE_ENV !== "development") {
+    return NextResponse.json({ error: "Not found" }, { status: 404 });
+  }
+
+  const hasUrl = Boolean(process.env.DATABASE_URL?.trim() || process.env.POSTGRES_URL?.trim());
+  const prisma = new PrismaClient();
+  try {
+    await prisma.$queryRaw`SELECT 1`;
+    return NextResponse.json({
+      ok: true,
+      databaseUrlConfigured: hasUrl,
+      hint: "Prisma connects; if auth still fails, check Google client id/secret and terminal [next-auth] logs.",
+    });
+  } catch (e: unknown) {
+    const message = e instanceof Error ? e.message : "Unknown error";
+    const publicHost = /Can't reach database server at `([\d.]+):(\d+)`/.exec(message);
+    const hint = publicHost
+      ? `No TCP route to Postgres at ${publicHost[1]}:${publicHost[2]} from this machine. In Coolify: confirm the DB service publishes that host port and Postgres listens on 0.0.0.0. On the cloud firewall (e.g. GCP), allow inbound TCP ${publicHost[2]} from your IP (or use VPN). Test: nc -zv ${publicHost[1]} ${publicHost[2]} or psql. Then npm run db:push from vibn-frontend.`
+      : "If the URL uses a Coolify internal hostname, it only works inside Docker. Otherwise check DATABASE_URL, firewall, and run npm run db:push.";
+    return NextResponse.json(
+      {
+        ok: false,
+        databaseUrlConfigured: hasUrl,
+        message,
+        hint,
+      },
+      { status: 500 }
+    );
+  } finally {
+    await prisma.$disconnect().catch(() => {});
+  }
+}