Persistence models (local playlists, watch history, bookmarks,
downloads) store only the best advertised thumbnail URL - usually
maxresdefault.jpg, which doesn't exist for many older videos and 404s.
Live API results survive this because views fall back through the full
quality chain, but toVideo() rebuilt videos with that single dead URL,
leaving placeholder covers.
Reconstruct the quality fallback chain from the stored YouTube-style
URL at read time (Thumbnail.fallbackChain), and rewrite playlist list
covers to the always-available hqdefault variant
(Thumbnail.reliableURL), since those views render a single URL without
fallback. Also expand the fabricated maxres URL in PipedAPI into a
full chain.
Proxied thumbnail URLs from Invidious/Piped/Yattee server expire over
time. Two paths were left holding stale URLs: the Video Info carousel
kept the original list copy even after fresh details arrived, and
downloaded videos rendered from the remote URL snapshot taken at
download time while the local thumbnail on disk was ignored.
Evict stale URLs from the Nuke cache when fresh video details load,
pass the fresh details through to the videoCard thumbnail, and resolve
downloads' thumbnails from the local file when localThumbnailPath is
set.
