feat(qq): bot can send and receive images and files (#1667)

Implement file upload and sending for QQ C2C messages

Reference: https://github.com/tencent-connect/botpy/blob/master/examples/demo_c2c_reply_file.py

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: chengyongru <chengyongru.ai@gmail.com>

tests/test_qq_channel.py

@@ -34,6 +34,7 @@ async def test_on_group_message_routes_to_group_chat_id() -> None:
         content="hello",
         group_openid="group123",
         author=SimpleNamespace(member_openid="user1"),
+        attachments=[],
     )
 
     await channel._on_message(data, is_group=True)