Bump mongoose from 8.6.2 to 8.6.3 in /backend

Bumps [mongoose](https://github.com/Automattic/mongoose) from 8.6.2 to 8.6.3.
- [Release notes](https://github.com/Automattic/mongoose/releases)
- [Changelog](https://github.com/Automattic/mongoose/blob/master/CHANGELOG.md)
- [Commits](Automattic/mongoose@8.6.2...8.6.3)

---
updated-dependencies:
- dependency-name: mongoose
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

backend/package-lock.json

@@ -28,7 +28,7 @@
     "dotenv": "^16.4.5",
     "express": "^4.21.0",
     "jsonwebtoken": "^9.0.2",
-    "mongoose": "^8.6.2",
+    "mongoose": "^8.6.3",
     "morgan": "^1.10.0"
   },
   "devDependencies": {