Stage 17 round 5 — backend/correctness bug fixes

- Resign on the opponent's turn: engine ResignSeat(seat) resigns a specific seat
  (not just toMove); game.Resign bypasses the turn check and forfeits the actor's seat.
- Quick-match cancel was a UI no-op (only stopped polling): add the full path
  (REST /lobby/cancel -> gateway lobby.cancel -> client) and clear the matchmaker's
  pending result on Cancel, so a cancelled search is dequeued (no 'already queued', no
  later robot-substituted game). NewGame dequeues on cancel and on abandon.
- Lobby win/loss: result.ts ranked by score, so a 0-0 resignation read as a win.
  The winner now takes rank 1 and the viewer is placed from rank 2 — matching the
  game-detail screen.
- Friend request to a robot: robots no longer block requests; the request stays
  pending and expires (friendRequestTTL), mirroring a human who ignores it.
- Nudge cooldown: ErrNudgeTooSoon now maps to a distinct nudge_too_soon code with a
  correct message; the chat nudge button disables during the hourly cooldown; the
  nudge note reads 'Waiting for your move!' (button keeps the Nudge action label).
Tests: engine/service off-turn resign, matchmaker cancel-clears-result, friend-to-robot
inttest, result.ts 0-0 resignation, nudge_too_soon mapping.

ui/src/lib/i18n/ru.ts

@@ -95,7 +95,8 @@ export const ru: Record<MessageKey, string> = {
 
   'chat.placeholder': 'Короткое сообщение…',
   'chat.send': 'Отправить',
-  'chat.nudge': 'Поторопить',
+  'chat.nudge': 'Жду вашего хода!',
+  'chat.nudgeAction': 'Поторопить',
   'chat.empty': 'Сообщений пока нет.',
   'chat.nudged': '{name} торопит вас',
 
@@ -156,6 +157,7 @@ export const ru: Record<MessageKey, string> = {
   'error.hint_unavailable': 'Подсказки недоступны.',
   'error.no_hint_available': 'Нет вариантов с вашим набором.',
   'error.chat_rejected': 'Сообщение отклонено (слишком длинное или содержит контакты).',
+  'error.nudge_too_soon': 'Не стоит торопить соперника так часто.',
   'error.game_finished': 'Эта игра уже завершена.',
   'error.not_a_player': 'Вы не участник этой игры.',
   'error.already_queued': 'Вы уже в очереди.',