Volume Widget Fix

Problem Description:

There were several issues with the audio volume handling in VLC:

The qt-max-volume setting was not properly synchronized across all UI components
When maximum volume was changed in preferences, the UI was not immediately updated
Volume callbacks were not being properly triggered when saving preferences
SoundWidget instances with volume sliders were not being refreshed after preference changes
Volume was not being properly saved and restored from configuration

When maximum volume setting is changed, all UI components are immediately updated
Volume controls now properly respect the maximum volume setting across all interfaces
Volume is properly saved and restored when configured to do so
User preferences for volume are maintained across sessions
All volume controls are consistent with the maximum volume setting
Callbacks are properly triggered when preferences are saved
UI refresh is immediate and comprehensive through toolbar rebuilding
Better memory management with proper callback cleanup in destructors