Filtering by a channel under the Mine scope returns nothing when that channel's
subscription is hidden (or you don't subscribe to it) — its videos only live in
the shared Library, since the Mine feed excludes hidden subscriptions by design.
Previously this left a bare 'No videos match these filters', which reads as a
bug when you know you're subscribed.
Add an empty-state hint + a 'View in Library' button (switches scope to all) when
there's a channel filter under Mine and zero results. Bilingual EN/HU.
Verified live: ?channel=<ColdFusion>&show=all under Mine shows the hint; the
button switches to Library and surfaces the 36 videos.