build(deps): bump zod-to-json-schema from 3.20.4 to 3.21.4 in /backend

Bumps [zod-to-json-schema](https://github.com/StefanTerdell/zod-to-json-schema) from 3.20.4 to 3.21.4.
- [Release notes](https://github.com/StefanTerdell/zod-to-json-schema/releases)
- [Changelog](https://github.com/StefanTerdell/zod-to-json-schema/blob/master/changelog.md)
- [Commits](https://github.com/StefanTerdell/zod-to-json-schema/commits)

---
updated-dependencies:
- dependency-name: zod-to-json-schema
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

backend/package.json

@@ -30,6 +30,6 @@
     "fastify": "^4.15.0",
     "fastify-zod": "^1.2.0",
     "zod": "^3.21.4",
-    "zod-to-json-schema": "^3.20.4"
+    "zod-to-json-schema": "^3.21.4"
   }
 }

backend/yarn.lock

@@ -3754,10 +3754,10 @@ yoga-layout-prebuilt@^1.9.6:
   dependencies:
     "@types/yoga-layout" "1.9.2"
 
-zod-to-json-schema@^3.17.1, zod-to-json-schema@^3.20.4:
-  version "3.20.4"
-  resolved "https://registry.yarnpkg.com/zod-to-json-schema/-/zod-to-json-schema-3.20.4.tgz#155f687c5a059fdc0f1bb3ff32d6e9200036b6f4"
-  integrity sha512-Un9+kInJ2Zt63n6Z7mLqBifzzPcOyX+b+Exuzf7L1+xqck9Q2EPByyTRduV3kmSPaXaRer1JCsucubpgL1fipg==
+zod-to-json-schema@^3.17.1, zod-to-json-schema@^3.21.4:
+  version "3.21.4"
+  resolved "https://registry.yarnpkg.com/zod-to-json-schema/-/zod-to-json-schema-3.21.4.tgz#de97c5b6d4a25e9d444618486cb55c0c7fb949fd"
+  integrity sha512-fjUZh4nQ1s6HMccgIeE0VP4QG/YRGPmyjO9sAh890aQKPEk3nqbfUXhMFaC+Dr5KvYBm8BCyvfpZf2jY9aGSsw==
 
 zod@^3.19.1, zod@^3.21.4:
   version "3.21.4"