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/index.html.erb

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+<h1>Match Administration</h1>
+
+<p><a href="/admin/matches/new">Enter New Match</a> | <a href="/admin/matches/upload">Upload CSV</a></p>
+
+<% if matches.any? %>
+  <table>
+    <thead>
+      <tr>
+        <th>ID</th>
+        <th>Date</th>
+        <th>Team 1</th>
+        <th>Score</th>
+        <th>Team 2</th>
+        <th>Score</th>
+        <th>Status</th>
+      </tr>
+    </thead>
+    <tbody>
+      <% matches.each do |match| %>
+        <tr>
+          <td><%= match.id %></td>
+          <td><%= match.played_at&.strftime('%Y-%m-%d %H:%M') %></td>
+          <td><%= match.team_1_p1_id %>/<%= match.team_1_p2_id %></td>
+          <td><%= match.team_1_score %></td>
+          <td><%= match.team_2_p1_id %>/<%= match.team_2_p2_id %></td>
+          <td><%= match.team_2_score %></td>
+          <td><%= match.status %></td>
+        </tr>
+      <% end %>
+    </tbody>
+  </table>
+<% else %>
+  <p>No matches entered yet.</p>
+<% end %>
+
+<p><a href="/admin/players">Manage Players</a></p>

app/templates/admin/matches/new.html.erb

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+<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>

app/templates/admin/matches/upload.html.erb

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+<h1>Upload Matches (CSV)</h1>
+
+<p>Upload a CSV file with the following columns:</p>
+<pre>
+played_at, team_1_p1_name, team_1_p2_name, team_1_score, team_2_p1_name, team_2_p2_name, team_2_score
+</pre>
+
+<form action="/admin/matches/process_upload" method="post" enctype="multipart/form-data">
+  <input type="hidden" name="_csrf_token" value="<%= csrf_token %>">
+  
+  <div>
+    <label for="csv_file">CSV File:</label>
+    <input type="file" id="csv_file" name="csv_file" accept=".csv" required>
+  </div>
+
+  <button type="submit">Upload</button>
+</form>
+
+<p><a href="/admin/matches">Back to Matches</a></p>
+
+<h2>Example CSV:</h2>
+<pre>
+played_at,team_1_p1_name,team_1_p2_name,team_1_score,team_2_p1_name,team_2_p2_name,team_2_score
+2026-03-26 10:00,Alice,Bob,10,Charlie,David,7
+2026-03-26 10:30,Alice,Bob,10,Charlie,David,7
+</pre>

app/templates/players/rankings.html.erb

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+<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>