rust-toolchain.toml and .cargo/config.toml hardcode x86_64-apple-darwin target, breaking Linux/CI/Docker builds

[abayomicornelius]

rust-toolchain.toml sets targets = [\"x86_64-apple-darwin\"] and .cargo/config.toml forces build.target = \"x86_64-apple-darwin\".

This means cargo build inside the Linux-based Dockerfile (FROM rust:1.78-slim) or any Linux CI runner will attempt to cross-compile for macOS and fail, since the target isn't installed and isn't appropriate for a container build. Remove the hardcoded target override (or make it conditional/local-only) so the project builds natively on Linux.