chore(backend): bump @libsql/client in /services/backend

Bumps [@libsql/client](https://github.com/libsql/libsql-client-ts/tree/HEAD/packages/libsql-client) from 0.14.0 to 0.15.9.
- [Release notes](https://github.com/libsql/libsql-client-ts/releases)
- [Changelog](https://github.com/tursodatabase/libsql-client-ts/blob/main/CHANGELOG.md)
- [Commits](https://github.com/libsql/libsql-client-ts/commits/v0.15.9/packages/libsql-client)

---
updated-dependencies:
- dependency-name: "@libsql/client"
  dependency-version: 0.15.9
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

services/backend/package.json

@@ -22,7 +22,7 @@
     "@fastify/cors": "^11.0.1",
     "@fastify/swagger": "^9.5.1",
     "@fastify/swagger-ui": "^5.2.3",
-    "@libsql/client": "^0.14.0",
+    "@libsql/client": "^0.15.9",
     "@lucia-auth/adapter-drizzle": "^1.1.0",
     "@node-rs/argon2": "^2.0.2",
     "@octokit/auth-app": "^8.0.1",