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/navigationContext.ts

@@ -23,8 +23,12 @@ export interface NavigationActions {
   /** Switch modules. Closes every open overlay first and pushes only once their history entries are
    *  back (`lib/history.closeOverlaysThenNavigate`), so over an open player the push lands a moment
    *  after the call; with nothing open it is synchronous. The requested page being already current
-   *  (with no channel page over it) pushes nothing — but the overlays still close. */
-  setPage: (next: Page) => void;
+   *  (with no channel page over it) pushes nothing — but the overlays still close.
+   *
+   *  `then` runs once the navigation has happened (the push made, or found unnecessary) — for a
+   *  request that belongs to the NEW entry, which over an open player does not exist yet at the
+   *  call (`lib/homeIntent`). */
+  setPage: (next: Page, then?: () => void) => void;
   openChannel: (id: string, name?: string) => void;
   closeChannel: () => void;
   enterYtSearch: (q: string) => void;