feat(player): a video's related videos, on demand beside it

The player shows what YouTube lists beside the video, without what the
user has watched or hidden. Wide, a Related tab beside the description;
stacked, a button beside the info opens them in a drawer. A row plays in
the same player (Back returns) and the list stays the opened video's.
A switch picks on-topic or Hungarian-trending lists, kept on the account.

Each related row says whether the user follows its channel; the row is
the video card's narrow form with its whole menu. VideoMenu moves to
features/video, where the player can reach it.

frontend/src/features/video/VideoCard.tsx

@@ -374,6 +374,8 @@ function VideoCard({
   menuOpen = false,
   navIndex,
   shelf = false,
+  narrow = false,
+  channelMark,
 }: {
   video: Video;
   view: FeedView;
@@ -397,6 +399,12 @@ function VideoCard({
   navIndex?: number;
   /** On a shelf (a horizontal strip): a one-line title over the channel alone (ui/mediaCardStyles). */
   shelf?: boolean;
+  /** The thumbnailed row in a side panel's ~20rem column: a smaller picture, and the "…" alone at the
+   *  row's end — the hover toggles leave no room for the title there, and every one of them is a row
+   *  of the menu. */
+  narrow?: boolean;
+  /** Something the list says about the channel (a "followed" mark), set before its name. */
+  channelMark?: ReactNode;
 }) {
   const { t, i18n } = useTranslation();
   const lang = i18n.language;
@@ -610,15 +618,46 @@ function VideoCard({
   const textBlock = (
     <>
       {title}
-      <div className="mt-0.5">{channelLink}</div>
+      <div className="mt-0.5">
+        {channelMark ? (
+          <div className="flex items-center gap-1 min-w-0">
+            {channelMark}
+            <div className="min-w-0">{channelLink}</div>
+          </div>
+        ) : (
+          channelLink
+        )}
+      </div>
       <div className="text-xs text-muted mt-0.5">
         {views}
         {views && " · "}
-        {published}
+        {/* The narrow row keeps the relative time and moves the date into its tooltip, as the small
+            card does: in a 20rem panel the full pair wrapped to a line of its own. */}
+        {narrow ? <RelativeTime at={video.published_at} /> : published}
       </div>
     </>
   );
 
+  if (spec.family === "row" && narrow) {
+    return (
+      <div
+        data-testid="video-card"
+        data-video-id={video.id}
+        {...menuProps?.(video)}
+        {...(navIndex !== undefined && navItemAttrs(navIndex))}
+        className={clsx(rowShell, "flex gap-2 p-1.5", watched && "opacity-55")}
+      >
+        <Thumb video={video} className="aspect-video shrink-0 w-24" onOpen={onOpen} small />
+        <div className="min-w-0 flex-1 flex flex-col">{textBlock}</div>
+        {more && (
+          <div className="shrink-0 self-start">
+            <MoreButton label={t("card.menu.more")} expanded={more.open} menuProps={more.props} />
+          </div>
+        )}
+      </div>
+    );
+  }
+
   if (spec.family === "row") {
     return (
       <div