feat(cli): completions, library/audio commands, server switcher

Embed bash and zsh completion scripts and add a `completions` subcommand.
Extend the player CLI (library, audio device, instant mix) and surface
`music_library` in snapshots. Add a shared active-server switcher in the
header and locales; instant mix can reseed the queue from CLI and UI.

src-tauri/Cargo.toml

@@ -52,6 +52,9 @@ symphonia-adapter-libopus = "0.2.7"
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"
 
+[target.'cfg(target_os = "linux")'.dependencies]
+zbus = { version = "5.9", default-features = false, features = ["blocking-api"] }
+
 [target.'cfg(windows)'.dependencies]
 windows = { version = "0.58", features = [
     "Win32_Foundation",