fix: resolve React frontend path issue causing white screen

- Problem: __dirname resolved to /data/home/alex/git/tilbudgivern in PM2
- Solution: Use absolute paths for frontend build serving
- Changed from path.join(__dirname, 'frontend/build') to absolute path
- Now serving from /home/alex/git/tilbudgivern/frontend/build
- JavaScript and CSS files load correctly with HTTP 200 status
- Fixes white screen issue in all tabs including tømrer and materiale priser

package.json

@@ -29,5 +29,8 @@
     "construction"
   ],
   "author": "Alex",
-  "license": "MIT"
+  "license": "MIT",
+  "devDependencies": {
+    "react-scripts": "^5.0.1"
+  }
 }