build(deps): bump sqlx from 0.7.4 to 0.8.1 in /backend

Bumps [sqlx](https://github.com/launchbadge/sqlx) from 0.7.4 to 0.8.1.
- [Changelog](https://github.com/launchbadge/sqlx/blob/main/CHANGELOG.md)
- [Commits](launchbadge/sqlx@v0.7.4...v0.8.1)

---
updated-dependencies:
- dependency-name: sqlx
  dependency-version: 0.8.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

backend/Cargo.lock

@@ -15,7 +15,7 @@ path = "src/bin/worker.rs"
 axum = { version = "0.7", features = ["multipart"] }
 tower_governor = "0.4"
 tokio = { version = "1", features = ["full"] }
-sqlx = { version = "0.7", features = ["runtime-tokio-rustls", "sqlite", "migrate"] }
+sqlx = { version = "0.8", features = ["runtime-tokio-rustls", "sqlite", "migrate"] }
 tower = { version = "0.4", features = ["util"] }
 tower-http = { version = "0.5", features = ["cors", "trace"] }
 serde = { version = "1.0", features = ["derive"] }