UI: unified design system, light/dark themes, redesigned pages and player UI

Tokens and components in styles.css, shared Ui (dialogs, toasts), icons,
bottom tab bar on mobile, keyboard/gamepad navigation, library shelf with
filters and conversion badges, hero game page, restyled player screens.
Games list now returns per-game version counts. Adds docs/UI_DESIGN.md.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

backend/app/permissions.py

@@ -7,6 +7,8 @@ PERMISSIONS: dict[str, str] = {
     "games.delete": "Удаление игр и любых версий",
     "versions.fork": "Создание своих версий (форков)",
     "versions.manage_any": "Управление чужими версиями",
+    "translations.edit": "Перевод игр в своих версиях",
+    "versions.publish": "Публикация версий и переводов, выбор главной версии",
     "users.manage": "Управление пользователями",
     "roles.manage": "Управление ролями",
 }
@@ -15,6 +17,7 @@ ALL = sorted(PERMISSIONS)
 
 SYSTEM_ROLES: dict[str, list[str]] = {
     "admin": ALL,
-    "moderator": ["games.play", "games.upload", "games.edit", "versions.fork"],
+    "moderator": ["games.play", "games.upload", "games.edit", "versions.fork",
+                  "translations.edit", "versions.publish"],
     "player": ["games.play"],
 }