feat(rust): add Cargo package management and build integration (fixes #100)

[jackmercy]

Summary

Fixes #100 — Fulfills all acceptance criteria for the [Cargo Package Management Integration ] bounty.

Implemented Capabilities (\Lux.Rust.Cargo):

1. Manifest Management (\lux/lib/lux/rust/cargo.ex):

   • Programmatic generation, manipulation, and validation of Cargo manifests (
     ew_manifest/2).
   • Adding and removing crate dependencies (\�dd_dependency/3,
     emove_dependency/2).
   • Parsing existing \Cargo.toml\ files into Elixir manifest structs (\parse_manifest/1).
   • Serializing manifest data into compliant TOML (\ o_toml/1).

2. Build Pipeline Integration:

   • Integration with \cargo build\ and \cargo build --release\ (\�uild/2).
   • Integrated test runner (\ est/2) and syntax/type checking (\check/2).

3. Package Caching & Version Management:

   • Configurable \CARGO_HOME\ caching via \configure_cache/1.
   • Semantic version pinning and optional feature flag specification.

4. Documentation & Unit Tests:

   • Comprehensive documentation guide in \lux/guides/language_support/rust_cargo_management.md.
   • Complete ExUnit test suite in \lux/test/unit/lux/rust/cargo_test.exs.

/claim #100