Improve playback settings UI controls on macOS

Standardized picker and button sizing with consistent alignment and control sizes. Added SettingsPickerModifier to all macOS pickers with menu style. Improved rate buttons with proper sizing and alignment. Added text truncation for stream descriptions to prevent overflow.

Shared/Views/SettingsPickerModifier.swift

@@ -15,6 +15,7 @@ struct SettingsPickerModifier: ViewModifier {
         #else
         content
             .labelsHidden()
+            .pickerStyle(.menu)
         #endif
     }
 }