build(deps-dev): bump @biomejs/biome (#222)

Bumps the minor-and-patch group in /backend with 1 update: [@biomejs/biome](https://github.com/biomejs/biome/tree/HEAD/packages/@biomejs/biome).


Updates `@biomejs/biome` from 2.3.15 to 2.4.1
- [Release notes](https://github.com/biomejs/biome/releases)
- [Changelog](https://github.com/biomejs/biome/blob/main/packages/@biomejs/biome/CHANGELOG.md)
- [Commits](https://github.com/biomejs/biome/commits/@biomejs/biome@2.4.1/packages/@biomejs/biome)

---
updated-dependencies:
- dependency-name: "@biomejs/biome"
  dependency-version: 2.4.1
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: minor-and-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

backend/package.json

@@ -35,7 +35,7 @@
     "zod": "^3.23.8"
   },
   "devDependencies": {
-    "@biomejs/biome": "^2.3.15",
+    "@biomejs/biome": "^2.4.1",
     "@types/node": "^25.2.3",
     "@types/nodemailer": "^6.4.21",
     "@types/supertest": "^6.0.2",