fix(home): shelf honours the Plex gate; hero unpins its origin; palette asks for a surprise

- A13: with Plex off, the Home shelf and the hero's comfort tier go YouTube-only like the rails
  beside them (owner's call: hide the tiles). The pins are kept; GET /pins still lists them.
- Reorder deals the listed pins into the slots they already hold, so a partial list (hidden Plex
  pins, a stale tab) no longer puts two pins on one position; repeats are ignored.
- A21: a comfort hero carries `pinned_from`, the shelf entry it was resolved from; its menu acts on
  that pin, so a pinned show's next episode offers "Unpin" instead of creating a second pin.
- B12: the palette's "Meglepetés" asks for the surprise tier (the next press leading with it); the
  rotation carries on from there.
- B13: the surprise token names the history entry it was requested for (minted by setPage's new
  `then`, after the push) and is dropped on any other entry, so a navigation that never mounted
  Home cannot replay it later.

frontend/src/components/comfortPin.tsx

@@ -49,7 +49,9 @@ export const pinPlex = (card: { id: string; type: string }): PinTarget => ({
 
 /** A unified discover card back to the thing it was pinned as — the inverse of the mapping in
  *  `app/discover/cards.py`. Null for a kind that cannot be pinned. */
-export function pinTargetForCard(card: DiscoverCard): PinTarget | null {
+export function pinTargetForCard(
+  card: Pick<DiscoverCard, "source" | "kind" | "id">,
+): PinTarget | null {
   if (card.source === "plex") return pinPlex({ id: card.id, type: card.kind });
   if (card.kind === "video") return pinVideo(card.id);
   if (card.kind === "channel") return pinChannel(card.id);