fix(ui): drop redundant Elapsed/Length cells; restore timeline

- Meta-grid reduced from 4 cells to 2 (State / Source). Elapsed and
  Length were duplicates of the timecodes already flanking the
  timeline. Added .meta-grid-2 modifier with a 2-column layout.
- Timeline was distorted by legacy rules: .progress-bar:hover did
  scaleY(1.4) (inflating the 2px hairline on hover) and the
  progress-fill::after handle defaulted to scale(0). Both are now
  forced via !important to keep the hairline flat and the copper
  handle always visible.
- progress-row uses minmax(0, 1fr) for the bar cell so it shrinks
  cleanly inside the grid.
- Removed unused meta.elapsed / meta.length keys from en.json + ru.json.
- Dead JS lookups for #meta-elapsed / #meta-length stay (cheap if-checks,
  no-op when DOM elements gone).

media_server/static/locales/ru.json

@@ -27,8 +27,6 @@
   "header.edition_sub": "Studio Reference Edition",
   "meta.state": "Состояние",
   "meta.source": "Источник",
-  "meta.elapsed": "Прошло",
-  "meta.length": "Длина",
   "player.title_unavailable": "Название недоступно",
   "player.source": "Источник:",
   "player.unknown_source": "Неизвестно",