deps(rust)(deps): bump the rust-core group

Updates the requirements on [thiserror](https://github.com/dtolnay/thiserror) and [itertools](https://github.com/rust-itertools/itertools) to permit the latest version.

Updates `thiserror` to 2.0.18
- [Release notes](https://github.com/dtolnay/thiserror/releases)
- [Commits](dtolnay/thiserror@1.0.0...2.0.18)

Updates `itertools` to 0.14.0
- [Changelog](https://github.com/rust-itertools/itertools/blob/master/CHANGELOG.md)
- [Commits](rust-itertools/itertools@v0.12.0...v0.14.0)

---
updated-dependencies:
- dependency-name: thiserror
  dependency-version: 2.0.18
  dependency-type: direct:production
  dependency-group: rust-core
- dependency-name: itertools
  dependency-version: 0.14.0
  dependency-type: direct:production
  dependency-group: rust-core
...

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

Author: dependabot[bot]

crates/signia-core/Cargo.toml

@@ -24,13 +24,13 @@ parallel = ["dep:rayon"]
 
 [dependencies]
 anyhow = "1.0"
-thiserror = "1.0"
+thiserror = "2.0"
 
 serde = { version = "1.0", features = ["derive"], optional = true }
 serde_json = { version = "1.0", optional = true }
 
 # Canonicalization helpers
-itertools = { version = "0.12", optional = true }
+itertools = { version = "0.14", optional = true }
 
 # Hashing
 sha2 = { version = "0.10", optional = true }