Add automated Linux and macOS setup and releases

[darwvin-dev]

What changed

Cross-platform dependency setup

• add one OS-dispatching npm run deps:runtime / npm run deps:build entrypoint
• support Arch, Debian/Ubuntu, Fedora, openSUSE, and macOS
• use official system package managers and show the exact package list before installation
• add dry-run, confirmation, non-interactive, and managed-host opt-out paths

macOS support

• use Apple Keychain through keyring's native macOS backend
• launch VNC connections through built-in macOS Screen Sharing
• install FreeRDP and sshpass through Homebrew for RDP and password SSH
• add an installer for unpacked .app bundles under ~/Applications
• build and publish .dmg artifacts on macos-14
• run Rust and frontend CI on macOS

Linux packaging

• bootstrap dependencies before AppImage installation
• declare runtime dependencies for Arch, Debian, and RPM packages

Validation

• npm test — 41 passed
• npm run build — passed
• Linux runtime/build bootstrap dry runs — passed
• all new shell scripts pass bash -n
• Tauri configuration discovery — passed
• git diff --check — passed

The macOS CI job added here is the authoritative native compile check because the current local workspace is Linux and has no Rust toolchain.