Bump path-to-regexp and express in /backend

Bumps [path-to-regexp](https://github.com/pillarjs/path-to-regexp) to 0.1.10 and updates ancestor dependency [express](https://github.com/expressjs/express). These dependencies need to be updated together.


Updates `path-to-regexp` from 0.1.7 to 0.1.10
- [Release notes](https://github.com/pillarjs/path-to-regexp/releases)
- [Changelog](https://github.com/pillarjs/path-to-regexp/blob/master/History.md)
- [Commits](pillarjs/path-to-regexp@v0.1.7...v0.1.10)

Updates `express` from 4.19.2 to 4.21.0
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/4.21.0/History.md)
- [Commits](expressjs/express@4.19.2...4.21.0)

---
updated-dependencies:
- dependency-name: path-to-regexp
  dependency-type: indirect
- dependency-name: express
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

backend/package.json

@@ -16,7 +16,7 @@
     "axios": "^1.6.7",
     "cors": "^2.8.5",
     "dotenv": "^16.4.5",
-    "express": "^4.19.2",
+    "express": "^4.21.0",
     "mongoose": "^8.2.1"
   },
   "devDependencies": {