REFACTOR(repo): simplify project structure

- Move services/nextjs/ to nextjs/
- Move Dockerfile.prod to Dockerfile at root
- Remove deploy/ folder (K8s manifests moved to K3S-HOME/web-apps)
- Remove .gitea/ workflows
- Update GitHub Actions for new structure
- Remove develop branch triggers

nextjs/next.config.mjs

@@ -0,0 +1,6 @@
+/** @type {import('next').NextConfig} */
+const nextConfig = {
+  output: 'standalone',
+};
+
+export default nextConfig;