Let admins delete tables from the lobby

Admins see a "削除" button on every table in the lobby. It calls the new
admin-only DELETE /api/tables/:id (404 for non-admins, same-origin only),
which closes the table the same way as when every human leaves. Players
and spectators still at the table are told "管理者がテーブルを削除しました。"

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

public/assets/table.js

@@ -54,7 +54,7 @@
     });
     socket.on('disconnect', () => { $('conn-lost').hidden = false; });
     socket.on('connect_error', () => { $('conn-lost').hidden = false; });
-    socket.on('table:closed', () => showNotFound(true));
+    socket.on('table:closed', (p) => showNotFound(true, p && p.reason));
     socket.on('table:state', (s) => {
       state = s;
       pending = false;
@@ -94,10 +94,11 @@
   }
 
   // closed: プレイヤーが全員退席してテーブルが閉じられた
-  function showNotFound(closed) {
+  function showNotFound(closed, reason) {
     if (closed) {
       $('not-found-title').textContent = 'テーブルが終了しました';
-      $('not-found-text').textContent = 'プレイヤーが全員退席したため、テーブルを閉じました。';
+      $('not-found-text').textContent =
+        reason === 'deleted' ? '管理者がテーブルを削除しました。' : 'プレイヤーが全員退席したため、テーブルを閉じました。';
     }
     $('main').hidden = true;
     $('action-bar').hidden = true;