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/plexSubUrl.ts

@@ -11,7 +11,8 @@ export type Sub =
   | { kind: "collections" } // browse-all-collections surface (header pill "Collection" mode)
   | { kind: "show"; id: string }
   | { kind: "season"; showId: string; seasonId: string }
-  | { kind: "player"; id: string; queue?: string[] }
+  // `fromStart`: the card's Restart (C5) — the first item plays from 0, not its resume point.
+  | { kind: "player"; id: string; queue?: string[]; fromStart?: boolean }
   | { kind: "info"; id: string }
   | { kind: "person"; name: string }
   | { kind: "playlist"; id: number }