Add explicit Alpine 3.21 main and community repository URLs to /etc/apk/repositories. Implement 5-attempt retry loop with 3-second delays for apk update and package installation to handle transient network failures during Docker builds.
Expand README with desktop platform requirements (Windows x86, macOS ARM), helper build commands, gateway utility scripts, and updated local test flow. Add realistic MVP usage section clarifying current platform build status, gateway configuration needs, and admin debug profile behavior with client private key handling.
