Update ContributionCalendar to adjust weeks displayed based on mobile view

- Modified the logic for determining the number of weeks to show in the ContributionCalendar component, reducing the count from 20 to 19 when in mobile view and not expanded.
- This change aims to optimize the calendar display for better usability on smaller screens.

src/components/ContributionCalendar.jsx

@@ -97,7 +97,7 @@ export default function ContributionCalendar({ data }) {
   }, []);
 
   // Determine how many weeks to show
-  const weeksToShow = isMobile && !expanded ? 20 : 52;
+  const weeksToShow = isMobile && !expanded ? 19 : 52;
   const startWeek = 52 - weeksToShow;
   const visibleDays = days.slice(startWeek * 7, 52 * 7);
   const visibleMonthLabels = monthLabels.filter(l => l.week >= startWeek);