Bump dotenv from 16.4.5 to 16.4.7 in /backend

Bumps [dotenv](https://github.com/motdotla/dotenv) from 16.4.5 to 16.4.7.
- [Changelog](https://github.com/motdotla/dotenv/blob/master/CHANGELOG.md)
- [Commits](motdotla/dotenv@v16.4.5...v16.4.7)

---
updated-dependencies:
- dependency-name: dotenv
  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

@@ -25,7 +25,7 @@
     "bcrypt": "^5.1.1",
     "bcryptjs": "^2.4.3",
     "cors": "^2.8.5",
-    "dotenv": "^16.4.5",
+    "dotenv": "^16.4.7",
     "express": "^4.21.0",
     "jsonwebtoken": "^9.0.2",
     "mongoose": "^8.7.0",