Create shared UI component library in packages/ui

[yashdev9274]

Description

Build out the shared UI component library in packages/ui following the existing patterns in apps/web/components/ui.

Expected Deliverables

• Set up packages/ui with proper exports
• Create base components:
  • Button
  • Input
  • Card
  • Modal/Dialog
  • Dropdown Menu
  • Avatar
  • Badge
• Add Storybook for component documentation
• Publish package for internal use

Requirements

• Use Tailwind CSS v4
• Follow existing cn() utility pattern
• Include TypeScript types
• Add basic component tests