fix(subscribe): preserve source identity when adding subscriptions

app/api/endpoints/media.py

@@ -366,6 +366,9 @@ async def seasons(
             )
             if mediainfo:
                 return _build_media_seasons(mediainfo, season)
+        # 明确来源的查询不能按标题切换到默认识别源，避免辅助 TMDB 信息替换主身份。
+        if media_source and source_media_id:
+            return []
     if title:
         meta = MetaInfo(title)
         if year: