Add unit tests for data file rotation utility functions

- Implement tests for writing data files with rotation, ensuring backups are created only on changes.
- Verify that old backups are rotated correctly and the maximum number of backups is maintained.
- Test restoration of backups while preserving the current state as a backup.
- Utilize Vitest for testing framework and manage temporary file storage during tests.

package.json

@@ -16,9 +16,12 @@
     "start": "nuxt start --port 3100",
     "postinstall": "nuxt prepare",
     "test": "vitest run",
+    "test:data-rotation": "vitest run tests/data-file-rotation.spec.ts",
     "check-security": "node scripts/verify-no-public-writes.js",
     "smoke-local": "BASE_URL=http://127.0.0.1:3100 node scripts/smoke-tests.js",
     "sync-public-data": "node scripts/sync-public-data.js",
+    "data-backups:list": "node scripts/data-backup-restore.js list",
+    "data-backups:restore": "node scripts/data-backup-restore.js restore",
     "hero:prepare": "node scripts/prepare-hero-variants.mjs",
     "import-spielplan": "node scripts/import-spielplan.js",
     "publish-spielplan": "node scripts/publish-imported-spielplan.js",