Add missing episodes feature: implement FindMissingEpisodes endpoint, update metadata providers to retrieve season episode counts, and enhance frontend components for displaying missing episodes report. Update translations for new UI elements.

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

@@ -2,6 +2,7 @@ import { apiRequest } from '@/shared/api/client'
 import type {
   CreatedIdResponse,
   MetadataCandidate,
+  MissingEpisodesReport,
   ShowAudience,
   ShowDto,
   ShowKind,
@@ -94,3 +95,8 @@ export function setShowPoster(showId: string, imageId: string | null) {
 export function refreshEpisodesMetadata(showId: string) {
   return apiRequest<number>(`/admin/metadata/shows/${showId}/refresh-episodes`, { method: 'POST' })
 }
+
+/** Отчёт: каких серий не хватает в загруженных сезонах (по данным источника). */
+export function findMissingEpisodes(showId: string) {
+  return apiRequest<MissingEpisodesReport>(`/admin/metadata/shows/${showId}/missing-episodes`)
+}