Add audio waveform toolbar for current clip

[mvineeta]

Introduce a new toolbar as a widget in the RPA mode that displays the audio waveform of the currently loaded clip. This visual waveform should dynamically update as the clip changes.

🎯 Feature Request:

• Add a new waveform widget as a docked toolbar similar to timeline and annotation toolbar.
• The widget should:
  • Render the audio waveform of the currently loaded clip.
  • Update automatically when a new clip is selected or loaded.
• Allow basic scrubbing or visual tracking of the current frame over the waveform (optional for later).
• Display should be minimal and responsive — a compact waveform that complements existing timeline functionality.

✅ Expected Behavior:

• When a clip with audio is loaded, the waveform appears in the toolbar widget.
• If the clip changes, the waveform is cleared and updated for the new clip.
• If the clip has no audio, the widget should display a placeholder or remain empty.
• The waveform view should align with the current frame in timeline for visual reference.

🔧 Implementation Notes:

• Could use a backend audio analysis library to extract waveform data (e.g., via ffmpeg, librosa, or OpenRV audio hooks).
• Rendering can be done via Qt widgets or HTML overlays (depending on performance/design).
• Caching waveform data for each clip may improve performance.
• Consider displaying a minimal horizontal waveform bar that spans the timeline width.