Bump thiserror from 1.0.69 to 2.0.12 in /backend

Bumps [thiserror](https://github.com/dtolnay/thiserror) from 1.0.69 to 2.0.12.
- [Release notes](https://github.com/dtolnay/thiserror/releases)
- [Commits](https://github.com/dtolnay/thiserror/compare/1.0.69...2.0.12)

---
updated-dependencies:
- dependency-name: thiserror
  dependency-version: 2.0.12
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

backend/Cargo.lock

@@ -2546,7 +2546,7 @@ dependencies = [
  "console_error_panic_hook",
  "insta",
  "reconcile",
- "thiserror 1.0.69",
+ "thiserror 2.0.12",
  "wasm-bindgen",
  "wasm-bindgen-test",
 ]
@@ -2576,7 +2576,7 @@ dependencies = [
  "serde_yaml",
  "sqlx",
  "sync_lib",
- "thiserror 1.0.69",
+ "thiserror 2.0.12",
  "tokio",
  "tower-http",
  "tracing",

backend/Cargo.toml

@@ -16,7 +16,7 @@ version = "0.3.9"
 
 [workspace.dependencies]
 serde = { version = "1.0.219", default-features = false, features = ["derive"] }
-thiserror = { version = "1.0.66", default-features = false  }
+thiserror = { version = "2.0.12", default-features = false  }
 
 [profile.release]
 codegen-units = 1