feat(抽奖): 活动删除按钮 + 格子数可选(8/9,默认8)

- 活动列表加"删除"(ConfirmButton→DELETE /activities/:id)
- activity-form 格子数选项 [8,9]，新建默认 8（原来写死只有 9）
- service: deleteLotteryActivity；i18n 删除文案

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/admin/public/assets/locales/en-US/lottery.json

@@ -265,5 +265,9 @@
     "tableTitle": "Draw records",
     "user": "User",
     "winOnly": "Won"
-  }
+  },
+  "delete": "Delete",
+  "deleteSuccess": "Deleted",
+  "confirmDeleteActivity": "Delete this activity?",
+  "confirmDeleteActivityDesc": "This permanently deletes the activity and its prizes. A running activity must be paused first. This cannot be undone."
 }

apps/admin/public/assets/locales/zh-CN/lottery.json

@@ -265,5 +265,9 @@
     "tableTitle": "抽奖记录",
     "user": "用户",
     "winOnly": "已中奖"
-  }
+  },
+  "delete": "删除",
+  "deleteSuccess": "删除成功",
+  "confirmDeleteActivity": "确定删除该活动吗？",
+  "confirmDeleteActivityDesc": "将永久删除该活动及其奖品。运行中的活动请先暂停。此操作不可撤销。"
 }