fix: standalone start script copies static files automatically

- scripts/start.js: copies .next/static to .next/standalone/.next/static
  before launching the standalone server (prevents CSS 404)
- package.json: start script now uses scripts/start.js
- Dockerfile: removed fragile manual better-sqlite3 copy
  (already included in standalone output)
- scripts/setup.sh: added local prod option for npm start

package.json

@@ -5,7 +5,7 @@
   "scripts": {
     "dev": "next dev",
     "build": "next build",
-    "start": "next start",
+    "start": "node scripts/start.js",
     "lint": "eslint"
   },
   "dependencies": {