feat(player): the side panel's list controls and watch toggle are glyphs on one line

The queue row (previous, count, next, auto-advance, loop) wrapped onto three lines in the
narrow side panel; glyph-only, it fits one. Mark watched joins the action icons as a toggle
(check / double check). Every control keeps its full name and shortcut as its tooltip and
accessible name; the docked bar keeps its labels. The related switch moves up to the toolbar
rung (12px), and its second side reads just "Trending".

frontend/src/features/player/RelatedVideos.tsx

@@ -164,7 +164,6 @@ export function RelatedVideos({
         value={region}
         onChange={setRegion}
         ariaLabel={t("player.related.region")}
-        size="sm"
         fullWidth
         className="mb-3"
       />