Add multi-league foundation

app/templates/leaderboard.html

@@ -4,11 +4,22 @@
   <div class="flex flex-col md:flex-row justify-between items-start md:items-center mb-6">
     <div>
       <h1 class="text-2xl md:text-3xl font-garamond font-bold text-irish-green">League Leaderboard</h1>
-      <p class="text-gray-600">See how your team ranks against the competition</p>
+      <p class="text-gray-600">
+        See how your team ranks in {{ selected_league.name if selected_league else "your league" }}
+      </p>
     </div>
     
     <div class="mt-4 md:mt-0">
-      <form method="get" action="/leaderboard/">
+      <form method="get" action="/leaderboard/" class="flex flex-col sm:flex-row gap-3">
+        <select name="league_id"
+                onchange="this.form.submit()"
+                class="border border-gray-300 rounded-md px-3 py-2 focus:outline-none focus:ring-2 focus:ring-irish-green bg-white">
+          {% for league in leagues %}
+            <option value="{{ league.id }}" {% if selected_league and selected_league.id == league.id %}selected{% endif %}>
+              {{ league.name }}
+            </option>
+          {% endfor %}
+        </select>
         <select name="timeframe" 
                 onchange="this.form.submit()" 
                 class="border border-gray-300 rounded-md px-3 py-2 focus:outline-none focus:ring-2 focus:ring-irish-green bg-white">