Bump rand from 0.8.5 to 0.9.0 in /backend

Bumps [rand](https://github.com/rust-random/rand) from 0.8.5 to 0.9.0.
- [Release notes](https://github.com/rust-random/rand/releases)
- [Changelog](https://github.com/rust-random/rand/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-random/rand/compare/0.8.5...0.9.0)

---
updated-dependencies:
- dependency-name: rand
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

backend/sync_server/Cargo.toml

@@ -29,7 +29,7 @@ chrono = { version = "0.4.40", features = ["serde"] }
 aide = { version = "0.13.4", features = ["axum", "axum-ws", "scalar", "axum-headers"] }
 schemars = { version = "0.8.21", features = ["chrono", "uuid1", "bytes"] }
 tracing = "0.1.41"
-rand = "0.8.5"
+rand = "0.9.0"
 sanitize-filename = "0.6.0"
 axum-jsonschema = { version = "0.8.0", features = ["aide"] }
 regex = "1.11.1"