Updated `.annot-sig-cb-wrapper` and related classes to improve
appearance, interactivity, and hover effects. Key changes include:
- Increased `border-radius` and adjusted `font-size`, `font-weight`,
and `padding` for a cleaner look.
- Replaced solid background and borders with gradient backgrounds
and updated `box-shadow` for modern styling.
- Added `cursor` property and refined `transition` effects for
smoother interactions.
- Updated hover and checked states with dynamic `filter` and
enhanced `box-shadow`.
- Hid `.annot-sig-cb` checkbox and improved `.annot-sig-cb__label`
readability with `letter-spacing`.