feat(cli): add logs mode with tail/follow and completion support (#337)

Introduce a dedicated --logs mode for CLI log viewing with --tail <lines> and
-f/--follow streaming from the normal/debug log channel, keep user-facing CLI
output free of timestamped log formatting, and update bash/zsh completions for
the new logs flags.

src-tauri/src/main.rs

@@ -85,6 +85,13 @@ fn main() {
     if psysonic_lib::cli::wants_info(&args) {
         psysonic_lib::cli::run_info_and_exit(&args);
     }
+    if psysonic_lib::cli::wants_logs(&args) {
+        psysonic_lib::cli::run_tail_and_exit(&args);
+    }
+    if psysonic_lib::cli::wants_tail(&args) {
+        eprintln!("NOT OK: --tail is only valid with --logs");
+        std::process::exit(2);
+    }
 
     psysonic_lib::run();
 }