Move leaderboard fetching to server-side

- Create src/lib/api.ts with fetchLeaderboard function for server use
- Update page.tsx to async component that fetches data at build/request time
- Pass fetched data to ClientPage as initialAppData prop
- Remove client-side useEffect and state management from ClientPage
- Reduce client bundle size (4.07kb → 2.99kb)
- Improve security by keeping API credentials server-only

src/lib/api.ts

@@ -0,0 +1,28 @@
+import { AppData } from './types';
+
+export async function fetchLeaderboard(): Promise<AppData | null> {
+  const API_BASE = process.env.NEXT_PUBLIC_API_BASE || '';
+  const SERVER_ID = process.env.NEXT_PUBLIC_SERVER_ID || '';
+  const ACCESS_TOKEN = process.env.NEXT_PUBLIC_ACCESS_TOKEN || '';
+
+  if (!API_BASE || !SERVER_ID || !ACCESS_TOKEN) {
+    console.warn('Missing API configuration');
+    return null;
+  }
+
+  try {
+    const res = await fetch(`${API_BASE}/server/${SERVER_ID}/leaderboard`, {
+      headers: {
+        "Access-Key": ACCESS_TOKEN
+      }
+    });
+    if (!res.ok) return null;
+    const data = await res.json();
+    // Treat empty leaderboard (no drivers) as null to fall back to defaults
+    if (!data || !data.drivers || data.drivers.length === 0) return null;
+    return data;
+  } catch (e) {
+    console.error("Failed to load leaderboard from API:", e);
+    return null;
+  }
+}