Add contributor leaderboard

Add types, hook, UI components, and integration for leaderboard showing top users with badges

src/hooks/useContributorLeaderboard.ts

@@ -0,0 +1,25 @@
+import { useQuery } from '@tanstack/react-query';
+import { supabase } from '@/lib/supabaseClient';
+import { LeaderboardData, TimePeriod } from '@/types/contributor';
+import { queryKeys } from '@/lib/queryKeys';
+
+export function useContributorLeaderboard(
+  limit: number = 50,
+  timePeriod: TimePeriod = 'all_time'
+) {
+  return useQuery({
+    queryKey: queryKeys.analytics.contributorLeaderboard(limit, timePeriod),
+    queryFn: async () => {
+      const { data, error } = await supabase.rpc('get_contributor_leaderboard', {
+        limit_count: limit,
+        time_period: timePeriod,
+      });
+
+      if (error) throw error;
+      
+      return data as unknown as LeaderboardData;
+    },
+    staleTime: 5 * 60 * 1000, // 5 minutes
+    refetchInterval: 5 * 60 * 1000, // Refresh every 5 minutes
+  });
+}