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/src/main.rs

@@ -13,5 +13,24 @@ fn main() {
             std::env::set_var("WEBKIT_DISABLE_COMPOSITING_MODE", "1");
         }
     }
+
+    let args: Vec<String> = std::env::args().collect();
+    if psysonic_lib::cli::wants_version(&args) {
+        psysonic_lib::cli::print_version();
+        return;
+    }
+    if psysonic_lib::cli::wants_help(&args) {
+        psysonic_lib::cli::print_help(
+            args.first().map(|s| s.as_str()).unwrap_or("psysonic"),
+        );
+        return;
+    }
+    if let Some(code) = psysonic_lib::cli::try_completions_dispatch(&args) {
+        std::process::exit(code);
+    }
+    if psysonic_lib::cli::wants_info(&args) {
+        psysonic_lib::cli::run_info_and_exit(&args);
+    }
+
     psysonic_lib::run();
 }