[Rust][Build] Link the native C API across supported platforms

[utilForever]

Parent: #137

Goal

Make Cargo builds locate or build the C API without duplicating native source configuration.

Scope

• Reuse CMake and the public C target
• Support documented static or shared linking mode
• Propagate actionable native build errors

Non-goals

• A second native build system
• Downloading unpublished binaries
• Supporting arbitrary external C library versions

Acceptance criteria

• Cargo builds the binding from a clean checkout on supported platforms.
• Native configuration remains in CMake.
• Link failures identify the missing target or dependency.

Verification

Build and link a minimal Rust binary on Ubuntu, macOS, and Windows CI jobs.