Add swipe gestures for mobile tabs (#219)

[Hollujay]

Description

Adds a reusable Tabs component with swipe gesture support for mobile devices. Users can now swipe left/right on touch screens to navigate between tab panels, while desktop users continue to click tab headers as before.

Motivation

Mobile users on narrow viewports need a native-feeling tab navigation experience. Swipe gestures provide intuitive, fast tab switching that matches platform conventions on iOS and Android.

Changes Made

New Files

• src/components/Tabs.jsx — Tab component with:

  • Touch swipe tracking (touchstart/touchmove/touchend with live translate during drag)
  • 50px swipe threshold before activating adjacent tab
  • Controlled (activeIndex prop) and uncontrolled modes
  • Click-to-switch on desktop via tab header buttons
  • Full ARIA tablist / tab / tabpanel roles, aria-selected, aria-controls, aria-labelledby
  • Proper keyboard tabIndex management

• src/components/Tabs.css — Dark-theme styles with:

  • Sliding indicator bar using CSS transform
  • Smooth transitions on tab switch
  • prefers-contrast: more/less media query support
  • Minimum 44×44px touch targets on tab headers (WCAG 2.5.5)

• test/components/Tabs.test.jsx — 15 tests covering:

  • Rendering all tab labels and default active state
  • Click-to-switch on desktop
  • aria-selected updates
  • onChange callback invocation
  • Controlled activeIndex via rerender
  • No-op when same tab is clicked
  • Swipe left to go next, swipe right to go previous
  • Boundary behavior (no swipe past first/last tab)
  • Sub-threshold swipe (no activation below 50px)
  • Accessible ARIA markup (ids, controls, labelledby)
  • Empty tabs array and custom className

• src/components/Tabs.stories.jsx — Storybook stories (default, two-tabs, controlled)

Modified Files

• README.md — Added Tabs to features list, project structure, and a new Tabs Component documentation section with usage example.

Testing

• All 15 new component tests pass
• Full test suite: existing failures are pre-existing (timeouts in integration/wallet tests, unrelated to this change)
• Storybook stories render correctly (default, two-tab, controlled variants)

Checklist

• Tests pass locally
• Code follows project style guidelines
• Documentation updated
• No breaking changes

Closes #219

[arisu6804]

Nice contribution! 🌟