fix(Calendar): 修复 FullCalendar CalendarApi.el 类型错误

- CalendarApi 接口不包含 el 属性，但运行时 Calendar 实例确实有此属性
- 添加类型断言 `as unknown as { el: HTMLElement }` 解决 TS2339 错误

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/components/Calendar/FullCalendarPro.tsx

@@ -343,7 +343,8 @@ export const FullCalendarPro: React.FC<FullCalendarProProps> = ({
     if (!calendarRef.current) return;
 
     // 获取所有日期单元格并更新内容
-    const calendarEl = calendarRef.current.getApi().el;
+    // CalendarApi 接口不包含 el 属性，但运行时 Calendar 实例确实有此属性
+    const calendarEl = (calendarRef.current.getApi() as unknown as { el: HTMLElement }).el;
     const dayCells = calendarEl?.querySelectorAll(".fc-daygrid-day");
 
     dayCells?.forEach((cell: Element) => {