Bump tokio from 1.43.0 to 1.43.1 in /backend

Bumps [tokio](https://github.com/tokio-rs/tokio) from 1.43.0 to 1.43.1.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-1.43.0...tokio-1.43.1)

---
updated-dependencies:
- dependency-name: tokio
  dependency-version: 1.43.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

backend/Cargo.lock

@@ -17,7 +17,7 @@ serde-inline-default = "0.2.0"
 sqlx = { version = "0.8.5", features = ["runtime-tokio-rustls", "sqlite", "time", "uuid"] }
 thiserror = "2.0.11"
 time = { version = "0.3.36", features = ["parsing", "serde"] }
-tokio = { version = "1.36.0", features = ["macros", "rt-multi-thread", "signal"] }
+tokio = { version = "1.43.1", features = ["macros", "rt-multi-thread", "signal"] }
 tower-http = { version = "0.6.1", features = ["cors", "fs", "trace"] }
 tracing = "0.1.40"
 tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }