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/PlexPlayer.session.dom.test.tsx

@@ -180,7 +180,7 @@ it("a seek that restarts the session is saved at its target while the new sessio
   });
   const beacon = vi.spyOn(api, "plexProgressBeacon").mockImplementation(() => {});
   await playingAt("/media/A", 1500);
-  fireEvent.click(screen.getByLabelText("plex.player.forward10"));
+  fireEvent.keyDown(document.body, { key: "ArrowRight" }); // the 10 s step
   await waitFor(() => expect(api.plexSession).toHaveBeenCalledTimes(2)); // a restart, not a native seek
   await tick();
   act(() => void window.dispatchEvent(new Event("pagehide")));
@@ -526,8 +526,8 @@ it("a seek made while a restart is pending wins over it", async () => {
   await waitFor(() => expect(video()?.getAttribute("src")).toBe("/media/A"));
   Object.defineProperty(video(), "seekable", { get: () => ({ length: 1, end: () => 100 }) });
   await playingAt("/media/A", 95);
-  fireEvent.click(screen.getByLabelText("plex.player.forward10")); // 105: past the buffer → restart
-  fireEvent.click(screen.getByLabelText("plex.player.rewind10")); // 95: inside the OLD buffer
+  fireEvent.keyDown(document.body, { key: "ArrowRight" }); // the 10 s step // 105: past the buffer → restart
+  fireEvent.keyDown(document.body, { key: "ArrowLeft" }); // 95: inside the OLD buffer
   await waitFor(() => expect(startsAsked("A")).toEqual([0, 105, 95]));
   await act(async () => pending.resolve({ mode: "direct", url: "/media/A2", start_s: 0 } as never));
   await tick();
@@ -594,7 +594,7 @@ describe("a session request that fails", () => {
       },
     });
     await playingAt("/media/A", 1500);
-    fireEvent.click(screen.getByLabelText("plex.player.forward10"));
+    fireEvent.keyDown(document.body, { key: "ArrowRight" }); // the 10 s step
     await screen.findByText("plex.player.errGeneric");
     await playingAt("/media/A", 1600); // the old stream plays on
     unmount();