chore(deps): update thiserror requirement from 1.0 to 2.0 in /backend

Updates the requirements on [thiserror](https://github.com/dtolnay/thiserror) to permit the latest version.
- [Release notes](https://github.com/dtolnay/thiserror/releases)
- [Commits](dtolnay/thiserror@1.0.0...2.0.17)

---
updated-dependencies:
- dependency-name: thiserror
  dependency-version: 2.0.17
  dependency-type: direct:production
...

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

Author: dependabot[bot]

backend/Cargo.toml

@@ -29,7 +29,7 @@ tokio = { version = "1.0", features = ["full"] }
 async-trait = "0.1"
 
 # Error handling
-thiserror = "1.0"
+thiserror = "2.0"
 anyhow = "1.0"
 
 # Logging