build(deps): bump @fastify/multipart from 9.4.0 to 10.0.0 in /backend

Bumps [@fastify/multipart](https://github.com/fastify/fastify-multipart) from 9.4.0 to 10.0.0.
- [Release notes](https://github.com/fastify/fastify-multipart/releases)
- [Commits](https://github.com/fastify/fastify-multipart/compare/v9.4.0...v10.0.0)

---
updated-dependencies:
- dependency-name: "@fastify/multipart"
  dependency-version: 10.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

backend/package.json

@@ -20,7 +20,7 @@
     "@fastify/cookie": "^11.0.2",
     "@fastify/cors": "^11.2.0",
     "@fastify/helmet": "^13.0.2",
-    "@fastify/multipart": "^9.4.0",
+    "@fastify/multipart": "^10.0.0",
     "@fastify/rate-limit": "^10.3.0",
     "@fastify/sensible": "^6.0.4",
     "@fastify/static": "^9.0.0",