feat(offline): hotseat in-game seat lock + host menu

Game.svelte drives a hotseat game:
- the seat-to-move's rack is replaced by an Unlock button when the seat
  is PIN-locked (board stays visible); canMove gates the move controls
  on the unlock; PinPad(verify) -> source.unlockSeat reveals it.
- the hint slot becomes a host button (hints off in hotseat), always
  enabled while the game runs (acts on a locked seat too). Master-PIN ->
  action sheet: skip current / exclude a player / end the game, each with
  a confirm + a fading check; terminate deletes and returns to the lobby.
- per-turn advance re-fetches the next seat's (locked) state; self-resign
  and chat are hidden (hotseat resign is a host action, no comms).
- gamesource: expose unlockSeat / verifyHostPin / hostAction on the local
  proxy. i18n hotseat.* (en + ru).

ui/src/lib/gamesource.ts

@@ -41,6 +41,11 @@ export const localSource = {
   create: (opts) => load().then((s) => s.create(opts)),
   list: () => load().then((s) => s.list()),
   delete: (id) => load().then((s) => s.delete(id)),
+  // Offline hotseat controls (no network equivalent): reveal a PIN-locked seat, and the host
+  // (referee) overrides gated by the master PIN.
+  unlockSeat: (id, pin) => load().then((s) => s.unlockSeat(id, pin)),
+  verifyHostPin: (id, pin) => load().then((s) => s.verifyHostPin(id, pin)),
+  hostAction: (id, pin, action, targetSeat) => load().then((s) => s.hostAction(id, pin, action, targetSeat)),
   // events must return the unsubscribe synchronously (the screen subscribes in onMount), so it wires
   // the real subscription once the engine loads and, until then, cancels a pending subscribe.
   events: (id, onEvent) => {
@@ -54,7 +59,8 @@ export const localSource = {
       unsub();
     };
   },
-} satisfies GameLoopSource & Pick<LocalSource, 'events' | 'create' | 'list' | 'delete'>;
+} satisfies GameLoopSource &
+  Pick<LocalSource, 'events' | 'create' | 'list' | 'delete' | 'unlockSeat' | 'verifyHostPin' | 'hostAction'>;
 
 /**
  * gameSource returns the source that runs the game with the given id: the local engine for a local