Refactor media preview functionality and update localization strings

Moved the mediaPreviewUrl function to the media API for better organization and clarity. Updated the MediaPanel component to include a preview feature for media assets, allowing users to view processed clips. Enhanced the UI to include a dialog for media previews and added corresponding localization strings in both English and Russian for the new preview functionality.

frontend/src/features/admin/interstitials/InterstitialsPanel.tsx

@@ -16,7 +16,8 @@ import { HlsVideo } from '@/shared/ui/hls-video'
 import { Input } from '@/shared/ui/input'
 import { BlockBuilder } from './BlockBuilder'
 import { ClipGroupPanel } from './ClipGroupPanel'
-import { listInterstitialBlocks, listInterstitials, mediaPreviewUrl } from './api'
+import { mediaPreviewUrl } from '@/features/admin/media/api'
+import { listInterstitialBlocks, listInterstitials } from './api'
 import { setDragItem } from './dnd'
 import { formatClock } from './format'
 

frontend/src/features/admin/interstitials/api.ts

@@ -16,8 +16,3 @@ export function importInterstitials(mediaAssetIds: string[]) {
     body: { mediaAssetIds },
   })
 }
-
-/** Плейлист обработанного ассета под admin-роутом (JWT) — грузится через hls.js. */
-export function mediaPreviewUrl(assetId: string) {
-  return `/api/admin/media/${assetId}/preview/index.m3u8`
-}