feat: modernize with Next.js 16 standalone output, remove redundant babel compiler, update postcss

- Remove babel-plugin-react-compiler (Next.js 16 has built-in reactCompiler)
- Update postcss to 8.5.25
- Add output: 'standalone' to next.config.ts for smaller/faster deployments
- Update ecosystem.config.cjs to use standalone server.js

ecosystem.config.cjs

@@ -2,8 +2,7 @@ module.exports = {
   apps: [
     {
       name: "next",
-      script: "pnpm",
-      args: "start",
+      script: ".next/standalone/server.js",
       exec_mode: "cluster",
       instances: 0,
       max_memory_restart: "512M",