Stage 8 polish: profile validation, finished-game UI, badge + Safari fixes

Owner-review follow-up on the Stage 8 branch:
- Friend code is copyable (📋 + toast). The lobby notification badge is fixed —
  it had inherited the hamburger-bar style — into a proper round count dot.
- Safari: min-width:0 on flex text inputs (friend code, profile, chat) so they
  shrink instead of pushing the adjacent button off-screen.
- Profile editing is validated on both the UI and the backend: display-name format
  (letters joined by single space/./_ separators, no leading/trailing/adjacent
  separators, <=32 runes), a UTC-offset timezone picker (account.ResolveZone parses
  ±HH:MM or a legacy IANA name), a 10-minute away grid capped at 12h (wrap-aware),
  and email format; Save is disabled and invalid fields red-bordered until valid.
  Language stays in Settings.
- In a game, an "add to friends" menu item flips to a disabled "request sent"; chat
  send/nudge became ⬆️/🛎️ icon buttons.
- A finished game drops its last-word highlight, hides Check word / Drop game,
  disables zoom, and draws an inert (greyed) footer instead of hiding it.

Tests: account validators (name/away/zone), UI profileValidation, e2e for the
finished-game footer/menu and the copy control. Docs (PLAN, ARCHITECTURE,
FUNCTIONAL +ru, UI_DESIGN) updated for the display-name rule, UTC-offset timezone
and the 12h away window.

ui/src/lib/i18n/ru.ts

@@ -179,6 +179,8 @@ export const ru: Record<MessageKey, string> = {
   'friends.enterCode': 'Есть код? Добавить друга',
   'friends.codePlaceholder': 'Код из 6 цифр',
   'friends.redeem': 'Добавить',
+  'friends.copy': 'Копировать',
+  'friends.codeCopied': 'Код скопирован.',
   'friends.added': 'Добавлен(а) {name}.',
   'friends.blockedList': 'Заблокированные',
   'friends.unblock': 'Разблокировать',
@@ -213,6 +215,7 @@ export const ru: Record<MessageKey, string> = {
 
   'game.exportGcg': 'Экспорт GCG',
   'game.gcgActiveOnly': 'Доступно после завершения игры.',
+  'game.requestSent': 'Запрос отправлен',
 
   'time.minutes': '{n} мин',
   'time.hours': '{n} ч',