chore(deps): bump fastify from 5.8.5 to 5.12.1

Bumps [fastify](https://github.com/fastify/fastify) from 5.8.5 to 5.12.1.
- [Release notes](https://github.com/fastify/fastify/releases)
- [Commits](fastify/fastify@v5.8.5...v5.12.1)

---
updated-dependencies:
- dependency-name: fastify
  dependency-version: 5.12.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

packages/agent-gateway/package.json

@@ -33,7 +33,7 @@
     "@pymodel/pythinker-code-oauth": "workspace:^",
     "@pymodel/transcript": "workspace:^",
     "bcryptjs": "^2.4.3",
-    "fastify": "^5.1.0",
+    "fastify": "^5.12.1",
     "pino": "^9.5.0",
     "semver": "^7.7.4",
     "smol-toml": "^1.6.1",