feat: add DatePicker module with calendar, range selection, and presets

[harshamittal]

• Add comprehensive DatePicker components (DatePicker, DateRangePicker, DatePickerWithPresets)
• Implement interactive demo page with form validation and error handling
• Add calendar popup with month/year navigation and preset selections
• Include real-time date range validation and past date prevention
• Add full accessibility support with ARIA labels and keyboard navigation
• Integrate with existing project architecture and module numbering system
• Add 13+ data-testid attributes for testing automation
• Update module numbering sequence (010-016) to accommodate new module
• Zero new dependencies - uses existing date-fns, lucide-react, react-day-picker
• Passes all linting checks and builds successfully

Files added:

• src/components/ui/date-picker.tsx
• src/pages/DatePickerDemo.tsx

Files modified:

• src/App.tsx (added route)
• src/pages/Index.tsx (added navigation)
• Module numbering updates (6 files)

@hugs Could you please take a look when you get a chance?

[hugs]

thank you, @harshamittal! i will take a look.