Add audio waveform toolbar widget for current clip

Introduce a new toolbar as a plugin in the RPA viewer UI 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.