feat: redesign media browser UI

- Root folder cards with hero-style layout and SVG icons
- Full-width thumbnails with aspect-ratio grid items
- List view column headers (Name, Bitrate, Duration, Size)
- Modernized breadcrumb with pill segments and overflow handling
- Proper skeleton shimmer replacing emoji hourglass on thumbnails
- Pagination shows "Showing X-Y of Z" item count
- Refined hover effects, animations, and visual hierarchy
- Download button revealed on row hover in list view
- Type badges hidden by default, shown on hover
- Localized new keys in en.json and ru.json

media_server/static/locales/ru.json

@@ -205,6 +205,11 @@
   "browser.folder_dialog.enabled": "Включено",
   "browser.folder_dialog.cancel": "Отмена",
   "browser.folder_dialog.save": "Сохранить",
+  "browser.list_header.name": "Название",
+  "browser.list_header.bitrate": "Битрейт",
+  "browser.list_header.duration": "Длительность",
+  "browser.list_header.size": "Размер",
+  "browser.showing_items": "Показано {from}\u2013{to} из {total}",
   "browser.download_error": "Не удалось скачать файл",
   "connection.reconnecting": "Соединение потеряно. Переподключение (попытка {attempt})...",
   "connection.lost": "Соединение потеряно. Сервер может быть недоступен.",