Fix prepare-release.sh incorrect directory reference

[jose-compu]

Description

scripts/prepare-release.sh references a directory called rust-port which appears to be a stale reference from before the project was renamed to chaincraft-rust.

Proposed Changes

• Audit prepare-release.sh for stale references
• Update paths to match the current repository structure
• Consider using $CARGO_MANIFEST_DIR or relative paths for robustness

Impact

Ensures the release preparation script works correctly.