Plain-JS Next config so the image boots without devDependencies

next start stops to install TypeScript when the config is a .ts file, which in
the container meant a yarn install into node_modules on every boot — slow
enough that the health check failed before the server answered.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

next.config.mjs

@@ -0,0 +1,9 @@
+/** @type {import('next').NextConfig} */
+// Plain JS, not TypeScript: `next start` in the production image has no
+// devDependencies, and a .ts config makes Next stop and install TypeScript —
+// with yarn, into a read-only-by-intent node_modules — before it will boot.
+const nextConfig = {
+  serverExternalPackages: ['better-sqlite3'],
+};
+
+export default nextConfig;