fix(#7904): QQ官方私聊主动推送不再因缺少缓存 msg_id 而跳过发送 (#7914)

* fix: QQ官方私聊主动推送不再因缺少缓存 msg_id 而跳过发送 (#7904)

- 私聊场景下 _send_by_session_common 在无缓存 msg_id 时提前 return，
导致重启后 cron 等主动推送的消息无法发送。
- 私聊主动推送不需要 msg_id，跳过此检查。

* test: 补充 QQ 官方群聊有缓存 msg_id 时正常发送的测试 (#7904)

* Delete tests/unit/test_qqofficial_adapter.py

---------

Co-authored-by: Weilong Liao <37870767+Soulter@users.noreply.github.com>

astrbot/core/platform/sources/qqofficial/qqofficial_platform_adapter.py

@@ -222,8 +222,9 @@ class QQOfficialPlatformAdapter(Platform):
         ):
             return
 
+        # 私聊主动推送不需要 msg_id，见 https://github.com/AstrBotDevs/AstrBot/issues/7904
         msg_id = self._session_last_message_id.get(session.session_id)
-        if not msg_id:
+        if not msg_id and session.message_type != MessageType.FRIEND_MESSAGE:
             logger.warning(
                 "[QQOfficial] No cached msg_id for session: %s, skip send_by_session",
                 session.session_id,