feat: Add admin pages for splits and tastings

- Create /admin/splits page showing all bottle splits
  - Stats: total splits, active, hosts, participants, volume
  - Filter by host, status (active/closed)
  - Progress bars showing reservation status

- Create /admin/tastings page showing all tasting notes
  - Stats: total tastings, users, avg rating, with notes, today
  - Filter by user, rating
  - Notes preview with star ratings

- Add navigation links to admin dashboard

src/app/admin/page.tsx

@@ -129,6 +129,18 @@ export default async function AdminPage() {
                         >
                             All Bottles
                         </Link>
+                        <Link
+                            href="/admin/splits"
+                            className="px-4 py-2 bg-purple-600 hover:bg-purple-700 text-white rounded-xl font-bold transition-colors"
+                        >
+                            All Splits
+                        </Link>
+                        <Link
+                            href="/admin/tastings"
+                            className="px-4 py-2 bg-pink-600 hover:bg-pink-700 text-white rounded-xl font-bold transition-colors"
+                        >
+                            All Tastings
+                        </Link>
                         <Link
                             href="/"
                             className="px-4 py-2 bg-zinc-900 dark:bg-zinc-100 text-white dark:text-zinc-900 rounded-xl font-bold hover:bg-zinc-800 transition-colors"