[Badge] Fix CVA defaultVariants, support ref as prop, and add variants

Summary

Improvements to the Badge component to fix a CVA configuration bug, improve component API consistency, and add flexibility.

Improvements

1. Fix defaultVariants placement in CVA

defaultVariants is incorrectly nested inside variants instead of being a sibling. CVA's defaults aren't working — the component only works because of manual fallbacks in the destructuring (variant = 'accent').

3. Make children optional

The type mandates children: ReactNode but a badge could be icon-only or dot-only.

5. Add dot/indicator variant

Common badge pattern for notification dots (no text, just a colored circle).

6. Add outline variant

Many design systems include an outline/bordered badge variant alongside solid and soft.

Moved to Cross-Cutting Issues

The following items have been moved to cross-cutting issues that address them across all components:

• Replace hardcoded CSS values with design tokens (#672)
• Forward HTML attributes (#674)

Start by locating the Badge component and its CVA configuration, then inspect how its current variants, defaults, children type, and ref handling are defined. The work is done when defaultVariants works without manual fallbacks, children can be omitted, ref support is consistent, and dot/indicator and outline variants are available.