Build Button, Input, Card, Badge components with variants

[phertyameen]

Issue #92: Build Button, Input, Card, Badge components with variants

Category: Theming
Repo: bridgelet (frontend + docs)

Description

Create a set of base UI components using class-variance-authority (CVA) for variant management: Button (primary, secondary, ghost, destructive), Input, Card, and Badge.

Acceptance Criteria

• Implementation complete
• Tests passing
• Docs updated
• Reviewed and merged