Add Elo rating system with match entry and CSV upload

- Implement EloCalculator service for 2v2 Euchre matches
- Create background job processing with GoodJob
- Add single match entry form
- Add CSV upload for batch match entry
- Create player rankings view
- Add database schema for matches and elo snapshots

app/templates/players/rankings.html.erb

@@ -0,0 +1,28 @@
+<h1>Player Rankings</h1>
+
+<% if players.any? %>
+  <table>
+    <thead>
+      <tr>
+        <th>Rank</th>
+        <th>Player</th>
+        <th>Elo Rating</th>
+        <th>Original Rating</th>
+      </tr>
+    </thead>
+    <tbody>
+      <% players.each_with_index do |player, index| %>
+        <tr>
+          <td><%= index + 1 %></td>
+          <td><%= player.name %></td>
+          <td><strong><%= player.current_elo %></strong></td>
+          <td><%= player.rating %></td>
+        </tr>
+      <% end %>
+    </tbody>
+  </table>
+<% else %>
+  <p>No players found.</p>
+<% end %>
+
+<p><a href="/admin/players">Admin</a></p>