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/lib/api.ts

@@ -28,7 +28,7 @@ import { feedApi } from "./api/feed";
 export type * from "./api/feed";
 import { discoverApi } from "./api/discover";
 export type * from "./api/discover";
-export { DISCOVER_BUDGETS, discoverCardKey } from "./api/discover";
+export { DISCOVER_BUDGETS, HERO_TIERS, discoverCardKey } from "./api/discover";
 export type * from "./api/tagModes";
 export {
   DEFAULT_TAG_MODES,