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] <support@github.com>

Author: dependabot[bot]

backend/Cargo.lock

@@ -16,7 +16,7 @@
     "alloc",
     "raw_value",
   ] }
-  tokio = { version = "1.47.1", features = [ "macros", "rt-multi-thread" ] }
+  tokio = { version = "1.48.0", features = [ "macros", "rt-multi-thread" ] }
   toml = { version = "0.9.8" }
   tower-http = { version = "0.6", features = [ "cors" ] }
   tracing = { version = "0.1" }