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/admin/matches/new.html.erb

@@ -0,0 +1,66 @@
+<h1>Enter New Match</h1>
+
+<form action="/admin/matches" method="post">
+  <input type="hidden" name="_csrf_token" value="<%= csrf_token %>">
+
+  <div>
+    <label for="played_at">Date/Time:</label>
+    <input type="datetime-local" id="played_at" name="played_at" required value="<%= Time.now.strftime('%Y-%m-%dT%H:%M') %>">
+  </div>
+
+  <fieldset>
+    <legend>Team 1</legend>
+    <div>
+      <label for="team_1_p1_id">Player 1:</label>
+      <select id="team_1_p1_id" name="team_1_p1_id" required>
+        <option value="">Select player...</option>
+        <% players.each do |player| %>
+          <option value="<%= player.id %>"><%= player.name %></option>
+        <% end %>
+      </select>
+    </div>
+    <div>
+      <label for="team_1_p2_id">Player 2:</label>
+      <select id="team_1_p2_id" name="team_1_p2_id" required>
+        <option value="">Select player...</option>
+        <% players.each do |player| %>
+          <option value="<%= player.id %>"><%= player.name %></option>
+        <% end %>
+      </select>
+    </div>
+    <div>
+      <label for="team_1_score">Score:</label>
+      <input type="number" id="team_1_score" name="team_1_score" min="0" max="10" required value="10">
+    </div>
+  </fieldset>
+
+  <fieldset>
+    <legend>Team 2</legend>
+    <div>
+      <label for="team_2_p1_id">Player 1:</label>
+      <select id="team_2_p1_id" name="team_2_p1_id" required>
+        <option value="">Select player...</option>
+        <% players.each do |player| %>
+          <option value="<%= player.id %>"><%= player.name %></option>
+        <% end %>
+      </select>
+    </div>
+    <div>
+      <label for="team_2_p2_id">Player 2:</label>
+      <select id="team_2_p2_id" name="team_2_p2_id" required>
+        <option value="">Select player...</option>
+        <% players.each do |player| %>
+          <option value="<%= player.id %>"><%= player.name %></option>
+        <% end %>
+      </select>
+    </div>
+    <div>
+      <label for="team_2_score">Score:</label>
+      <input type="number" id="team_2_score" name="team_2_score" min="0" max="10" required value="7">
+    </div>
+  </fieldset>
+
+  <button type="submit">Save Match</button>
+</form>
+
+<p><a href="/admin/matches">Back to Matches</a></p>