Fixed the Docker cross-compilation pipeline to work on ARM hosts (like Apple Silicon Macs). The Dockerfile now uses conditional platform targeting so it can build Windows and Linux x86_64 binaries regardless of the host architecture. Added a build.sh script for non-Windows environments that skips the lint Docker image.

Also added auto-creation of the config file — if ~/.project-switch.yml doesn’t exist when the program starts, it creates one with sensible defaults instead of erroring. Added cargo registry caching in the Docker build to speed up repeated builds.