build(deps): bump fastify from 5.8.4 to 5.8.5 in /backend

Bumps [fastify](https://github.com/fastify/fastify) from 5.8.4 to 5.8.5.
- [Release notes](https://github.com/fastify/fastify/releases)
- [Commits](https://github.com/fastify/fastify/compare/v5.8.4...v5.8.5)

---
updated-dependencies:
- dependency-name: fastify
  dependency-version: 5.8.5
  dependency-type: direct:production
...

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backend/package.json

@@ -30,7 +30,7 @@
     "argon2": "^0.44.0",
     "dotenv": "^17.4.2",
     "drizzle-orm": "^0.45.2",
-    "fastify": "^5.8.4",
+    "fastify": "^5.8.5",
     "fastify-plugin": "^5.0.1",
     "jose": "^6.2.2",
     "nodemailer": "^8.0.5",