feat: add prettier for code formatting

refactor: update route for downloader to apps/downloader

chore: remove unused filler model files

refactor: delete Default layout component and its imports

frontend/package.json

@@ -35,6 +35,7 @@
     "eslint-plugin-react-refresh": "^0.4.20",
     "globals": "^16.3.0",
     "orval": "^7.13.2",
+    "prettier": "^3.7.4",
     "typescript": "~5.8.3",
     "typescript-eslint": "^8.39.1",
     "vite": "^7.1.2"