add fallback thumb for queue, add ta_download to thumb validator

backend/download/src/queue.py

@@ -359,6 +359,9 @@ class PendingList(PendingIndex):
         if "thumbnail" in video_data:
             return video_data["thumbnail"]
 
+        if video_data.get("thumbnails"):
+            return video_data["thumbnails"][-1]["url"]
+
         return None
 
     def __extract_published(self, video_data) -> str | int | None:

backend/download/src/thumbnails.py

@@ -265,7 +265,7 @@ class ValidatorCallback:
     def run(self):
         """run the task for page"""
         print(f"{self.index_name}: validate artwork")
-        if self.index_name == "ta_video":
+        if self.index_name in ["ta_video", "ta_download"]:
             self._validate_videos()
         elif self.index_name == "ta_channel":
             self._validate_channels()
@@ -325,6 +325,13 @@ class ThumbValidator:
             },
             "name": "ta_playlist",
         },
+        {
+            "data": {
+                "query": {"term": {"status": {"value": "pending"}}},
+                "_source": ["youtube_id", "vid_thumb_url"],
+            },
+            "name": "ta_download",
+        },
     ]
 
     def __init__(self, task=False):