feat: 企微测试消息端点 + 调度器 msgfmt 优化

- 新增 POST /api/wecom/test-message 测试端点(需 director)
- 调度器仅推已绑定 wecom_userid 的经理
- wecom.py 已支持 markdown/模板卡片消息

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

backend/app/api/wecom.py

@@ -124,6 +124,19 @@ async def send_announcement(
     return {"success": success, "sent_to": len(wecom_ids)}
 
 
+@router.post("/test-message")
+async def test_message(
+    wecom_userid: str,
+    current_user: dict = Depends(require_director),
+):
+    """Send a test message to a specific wecom_userid for debugging."""
+    success = await wecom_client.send_text_message(
+        [wecom_userid],
+        "🧪 企迹周报系统 — 测试消息\n\n如果您收到此消息，说明企微消息推送配置成功！"
+    )
+    return {"success": success, "sent_to": wecom_userid}
+
+
 @router.post("/trigger-daily-check")
 async def trigger_daily_check(
     current_user: dict = Depends(require_director),