[Build] Add mobile responsive design - portrait mode support

## GitHub Update **Repository:** [MKWcorp/sales-race-beautycenter](https://github.com/MKWcorp/sales-race-beautycenter) **Author:** multimediadrw **Date:** 12/8/2025, 10:55:35 AM **Commit:** [`02f1f43`](https://github.com/MKWcorp/sales-race-beautycenter/commit/02f1f43ddea680126b716a18aedc20e4cd0f2381) ### Commit Message Add mobile responsive design - portrait mode support Features: - Full mobile support without rotation needed - Responsive header with smaller icons and text - Compact filter buttons (4 buttons fit on mobile) - Period selectors wrap on mobile (flex-wrap) - Stats cards use grid layout on mobile (2 columns) - Leaderboard rows stack vertically on mobile - Achievement badge moves inline on mobile - Footer stacks on mobile with shorter labels - All touch targets sized appropriately Breakpoints: - Mobile: base (320px+) - Tablet: md (768px+) - Desktop: lg (1024px+) Technical: - Text sizes: text-[8px] → md:text-[10px] → lg:text-xs - Icons: w-2 h-2 → md:w-2.5 md:h-2.5 → lg:w-3 lg:h-3 - Padding/gaps: smaller on mobile, larger on desktop - Month names abbreviated on mobile weekly filter --- _This story was imported from historical commits._