chore(deps): bump tokio from 1.47.1 to 1.48.0 in /backend

Bumps [tokio](https://github.com/tokio-rs/tokio) from 1.47.1 to 1.48.0.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-1.47.1...tokio-1.48.0)

---
updated-dependencies:
- dependency-name: tokio
  dependency-version: 1.48.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

backend/Cargo.lock

@@ -32,7 +32,7 @@ serde = { version = "1.0.228", features = ["derive"] }
 serde_json = { version = "1.0.145" }
 thiserror = { version = "2.0.17" }
 tracing = { version = "0.1.41" }
-tokio = { version = "1.47.1", features = [
+tokio = { version = "1.48.0", features = [
     "macros",
     "time",
     "net",