Add lean review issues: up to two problem tags plus short note.

Persist review_issues, enforce max two on save, and show issue breakdown in stats.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/templates/records_stats.html

@@ -75,7 +75,7 @@
   <div class="card">
     <div class="muted">入场形式标注</div>
     <div class="stat" style="font-size:22px">{{ stats.annotated }} <span class="muted" style="font-size:14px">/ {{ stats.total }}</span></div>
-    <div class="muted" style="margin-top:6px">未标注 {{ stats.unannotated }}</div>
+    <div class="muted" style="margin-top:6px">未标注 {{ stats.unannotated }} · 问题标注 {{ stats.issue_tagged }}</div>
   </div>
 </div>
 
@@ -185,6 +185,33 @@
   </div>
 </div>
 
+<div class="card" style="margin-top:14px">
+  <h3>按主要问题</h3>
+  <p class="muted" style="margin:0 0 10px">一笔可勾 1～2 个问题，会分别计入对应行。</p>
+  <table>
+    <thead>
+      <tr>
+        <th>问题</th><th>笔数</th><th>胜率</th><th>盈亏</th><th>平均持仓</th>
+      </tr>
+    </thead>
+    <tbody>
+      {% for g in stats.by_issue %}
+      <tr>
+        <td>{{ g.label }}</td>
+        <td>{{ g.count }}</td>
+        <td>{{ '%.1f'|format(g.win_rate) }}%</td>
+        <td style="color:{% if g.profit>0 %}var(--green){% elif g.profit<0 %}var(--red){% else %}inherit{% endif %}">
+          {{ '%.2f'|format(g.profit) }}
+        </td>
+        <td class="muted">{{ g.avg_hold }}</td>
+      </tr>
+      {% else %}
+      <tr><td colspan="5" class="muted">暂无问题标注</td></tr>
+      {% endfor %}
+    </tbody>
+  </table>
+</div>
+
 <div class="card" style="margin-top:14px">
   <h3>按机器</h3>
   <table>