- Convert HighlightsPanel buttons to use IconButton component
- Add style prop support to IconButton for custom styling
- Remove redundant CSS for old button classes (level-toggle-btn, refresh-highlights-btn, etc.)
- Keep only highlight-level-toggles container styling
- Consistent button appearance across left and right sidebars
- DRY: Single IconButton component handles all sidebar buttons
- Apply color style directly to both icons in collapsed highlights button
- Update CSS to use color-agnostic pulse animation (opacity/scale)
- Remove hardcoded yellow color and drop-shadow from glow effect
- Update HighlightsPanelCollapsed to accept settings prop
- Apply highlightColorMine to the expand button icon and text
- Pass settings through HighlightsPanel and ThreePaneLayout