feat(design): players on touch and the C5 control set, restart on the card (E28 S3f2)

Plex player: a finger's tap on the picture only shows or hides the controls,
the hide timer starts with playback, a double-tap on a side third skips 10 s,
the seek bar is a 2.75rem touch-none hit area with its head shown on touch.
The row is play/pause, Back by position, Next only with a next item, mute,
time, tracks, a fixed ⋯ (settings, media info, stats, shortcuts, download)
and fullscreen; Stop, Restart and the ±10 s buttons are gone.

A started card shows the video card's Continue + Restart pair (one shared
MediaResumeButtons, beside the picture's button), and its menu lists the
restart; the player opens that item at 0 (fromStart). YouTube modal: the
description opens from an ⓘ, the queue arrows sit inside the screen.

frontend/src/components/PlexDiscover.tsx

@@ -31,6 +31,7 @@ function CardRail({
   onSeeAll,
   cards,
   onOpenCard,
+  onRestartCard,
   onInfoCard,
   onToggleWatched,
   action,
@@ -41,6 +42,7 @@ function CardRail({
   onSeeAll?: () => void;
   cards: PlexCard[];
   onOpenCard: (c: PlexCard) => void;
+  onRestartCard: (c: PlexCard) => void;
   onInfoCard: (c: PlexCard) => void;
   onToggleWatched: (c: PlexCard) => void;
   action?: ReactNode; // optional header control (e.g. the Surprise-me reshuffle button)
@@ -48,7 +50,7 @@ function CardRail({
   // One menu per rail (see ui/ContextMenu), not one per poster.
   const menu = useContextMenu<PlexCard>();
   const actions = usePlexCardActions(
-    { onOpen: onOpenCard, onInfo: onInfoCard, onToggleWatched },
+    { onOpen: onOpenCard, onRestart: onRestartCard, onInfo: onInfoCard, onToggleWatched },
     menu.open,
   );
   const heading =
@@ -76,6 +78,7 @@ function CardRail({
               card={c}
               navIndex={i}
               onOpen={() => onOpenCard(c)}
+              onRestart={() => onRestartCard(c)}
               onToggleWatched={onToggleWatched}
               onAdd={actions.add}
               menuProps={menu.triggerProps}
@@ -93,12 +96,14 @@ function CardRail({
 export default function PlexDiscover({
   scope,
   onOpenCard,
+  onRestartCard,
   onInfoCard,
   onGenre,
   onSeeAllRecent,
 }: {
   scope: string;
   onOpenCard: (c: PlexCard) => void;
+  onRestartCard: (c: PlexCard) => void;
   onInfoCard: (c: PlexCard) => void;
   onGenre: (genre: string) => void;
   onSeeAllRecent: () => void;
@@ -184,7 +189,7 @@ export default function PlexDiscover({
     return <p className="text-muted text-sm">{t("plex.discover.empty")}</p>;
   }
 
-  const railProps = { onOpenCard, onInfoCard, onToggleWatched: toggleWatched };
+  const railProps = { onOpenCard, onRestartCard, onInfoCard, onToggleWatched: toggleWatched };
 
   return (
     <div>