* feat(widgets): add WnCarouselIndicator component
Implement carousel indicator widget for showing position in paginated content.
- Active dot expands (28px) with primary fill color
- Inactive dots are circular (8px) with secondary fill color
- Directional bounce animation using elasticOut curve (600ms)
- Fast color transition (150ms) for smooth deactivation
- 8px gap between indicator dots
Closes#103
* fix: use .r for border radius and remove context anti-pattern
- Change BorderRadius.circular(4.h) to BorderRadius.circular(4.r)
- Remove stored BuildContext field in _InteractiveCarouselIndicator