Switch to web_embedded player client

web_embedded: supports cookies, no Node.js/JS runtime needed, 23 video
formats available. android_vr was skipped by yt-dlp when cookies are
present since that client doesn't support cookie auth.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/settings.py

@@ -247,7 +247,7 @@ def ytdlp_test(
             "yt-dlp",
             "https://www.youtube.com/watch?v=dQw4w9WgXcQ",
             "--dump-json", "--no-download", "--no-playlist",
-            "--extractor-args", "youtube:player_client=android_vr",
+            "--extractor-args", "youtube:player_client=web_embedded",
             *cookie_args,
         ],
         capture_output=True, text=True, timeout=30,