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/lib/zLayer.contract.test.ts

@@ -46,7 +46,7 @@ describe("the Plex player's layers", () => {
     const popovers = classes(
       /\bbottom-full\b.*\bbg-media-chrome\b|\bbg-media-chrome\b.*\bbottom-full\b/,
     );
-    expect(popovers).toHaveLength(2);
+    expect(popovers).toHaveLength(3); // tracks, the ⋯ menu (C5), the settings panel
     for (const c of popovers) expect(c).toMatch(/\bz-menu\b/);
   });