Publish silvestre-core to crates.io

[enzoftware]

Description

Prepare and publish the silvestre-core crate to crates.io for the Rust ecosystem.

Tasks

• Fill in Cargo.toml metadata: description, license (MIT/Apache-2.0), repository, keywords, categories
• Add LICENSE file(s) to repository root
• Ensure all public API is documented
• Run cargo publish --dry-run to verify
• Publish to crates.io

Acceptance Criteria

• cargo publish --dry-run succeeds
• Crate metadata is complete and accurate
• License is clearly specified
• Published crate can be added as a dependency by external projects