Refresh waveform context menu after UI language changes

[pdjdev]

Problem

After changing the UI language via Options > Choose UI Language..., most controls were updated immediately, but the waveform context menu continued to use the previous language.

The updated menu text only appeared after closing and restarting Subtitle Edit.

Cause & Fix

The AudioVisualizer control is reused when the main layout is rebuilt. However, its context menu was created inside the vm.AudioVisualizer == null block, so the menu labels were only initialized when the control was first created.

The fix rebuilds the waveform context menu whenever the layout is rebuilt. The existing AudioVisualizer instance and its event subscriptions are preserved; only the context menu and accessible name are refreshed using the current UI language.

Screenshots

Before	After
The context menu remains in the previous language	The context menu updates immediately after changing the UI language
2026-07-0700-27-13-ezgif.com-mute-video.mp4	2026-07-0700-27-13-ezgif.com-mute-video.1.mp4

Testing

Tested on Windows 11 x64 (local Release build).