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

ui/src/lib/i18n/en.ts

@@ -408,6 +408,16 @@ export const en = {
   'hotseat.hostPlaysTitle': 'Are you playing too?',
   'hotseat.hostPlaysYes': 'Yes, I play',
   'hotseat.hostPlaysNo': 'No',
+  'hotseat.unlock': 'Unlock',
+  'hotseat.unlockTitle': 'Unlock: {name}',
+  'hotseat.turnOf': 'Turn: {name}',
+  'hotseat.host': 'Host',
+  'hotseat.skip': 'Skip the current turn',
+  'hotseat.exclude': 'Exclude a player:',
+  'hotseat.terminate': 'End the game',
+  'hotseat.askSkip': "Skip {name}'s turn?",
+  'hotseat.askExclude': 'Remove {name} from the game?',
+  'hotseat.askTerminate': 'End the game with no result?',
 } as const;
 
 export type MessageKey = keyof typeof en;

ui/src/lib/i18n/ru.ts

@@ -408,4 +408,14 @@ export const ru: Record<MessageKey, string> = {
   'hotseat.hostPlaysTitle': 'Принимаете участие в игре?',
   'hotseat.hostPlaysYes': 'Да, играю',
   'hotseat.hostPlaysNo': 'Нет',
+  'hotseat.unlock': 'Разблокировать',
+  'hotseat.unlockTitle': 'Разблокировать: {name}',
+  'hotseat.turnOf': 'Ход: {name}',
+  'hotseat.host': 'Ведущий',
+  'hotseat.skip': 'Пропустить ход',
+  'hotseat.exclude': 'Исключить игрока:',
+  'hotseat.terminate': 'Отменить партию',
+  'hotseat.askSkip': 'Пропустить ход игрока {name}?',
+  'hotseat.askExclude': 'Удалить {name} из игры?',
+  'hotseat.askTerminate': 'Отменить партию без результата?',
 };