Add restore functionality for template management and enhance related components

Implemented a new endpoint for restoring templates to their last applied state, allowing users to revert changes made since the last application. Updated the ScheduleTemplate class to include a snapshot of the last applied state, enabling rollback capabilities. Enhanced the frontend with a restore button in the ChannelDetail component, providing users with a confirmation prompt before executing the restore action. Localization updates were made to support new UI strings in both English and Russian, improving the overall user experience in template management.

frontend/src/features/admin/channels/ChannelDetail.tsx

@@ -1,6 +1,6 @@
 import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
 import { Link } from '@tanstack/react-router'
-import { ChevronLeft, Send } from 'lucide-react'
+import { ChevronLeft, Send, Undo2 } from 'lucide-react'
 import { useState } from 'react'
 import { useTranslation } from 'react-i18next'
 import { listAllMedia } from '@/features/admin/media/api'
@@ -11,7 +11,13 @@ import { Badge } from '@/shared/ui/badge'
 import { Button } from '@/shared/ui/button'
 import { Card, CardContent } from '@/shared/ui/card'
 import { toast } from '@/shared/ui/toast-store'
-import { applyChannelTemplate, getChannel, getChannelTemplate, getSchedule } from './api'
+import {
+  applyChannelTemplate,
+  getChannel,
+  getChannelTemplate,
+  getSchedule,
+  restoreChannelTemplate,
+} from './api'
 import { ApplyDialog } from './components/ApplyDialog'
 import { BumperCard } from './components/BumperCard'
 import { EntryTraceDialog } from './components/EntryTraceDialog'
@@ -70,6 +76,18 @@ export function ChannelDetail({ channelId }: Readonly<{ channelId: string }>) {
     onError,
   })
 
+  const restoreMutation = useMutation({
+    mutationFn: () => restoreChannelTemplate(channelId),
+    onSuccess: (result) => {
+      toast.success(t('admin.channels.restored', { count: result.slots }))
+      // Ссылка на удалённую группу или стык вернуться не может — говорим об этом прямо.
+      if (result.droppedRefs > 0)
+        toast.error(t('admin.channels.restoreDropped', { count: result.droppedRefs }))
+      invalidate()
+    },
+    onError,
+  })
+
   if (isLoading || !channel) return <p className="text-muted-foreground">{t('common.loading')}</p>
 
   return (
@@ -89,13 +107,31 @@ export function ChannelDetail({ channelId }: Readonly<{ channelId: string }>) {
         </div>
       </div>
 
-      {/* Правка правил эфира не двигает — применение отдельной кнопкой. */}
+      {/* Правка правил эфира не двигает — применение отдельной кнопкой. Рядом откат: правки
+          сетки правятся на месте, и без этой кнопки вернуть «как в эфире» было бы нечем. */}
       {template?.hasPendingChanges && (
         <div className="flex flex-wrap items-center justify-between gap-3 rounded-md border border-amber-500/50 bg-amber-500/10 px-4 py-2 text-sm">
           <span>{t('admin.channels.pendingChanges')}</span>
-          <Button size="sm" disabled={applyMutation.isPending} onClick={() => setApplyOpen(true)}>
-            <Send className="h-4 w-4" /> {t('admin.channels.apply')}
-          </Button>
+          <div className="flex flex-wrap items-center gap-2">
+            {/* Кнопки отката нет, пока сетку ни разу не применяли: возвращаться некуда. */}
+            {template.canRestore && (
+              <Button
+                size="sm"
+                variant="outline"
+                disabled={restoreMutation.isPending}
+                onClick={() => {
+                  // Откат необратим — он стирает всё, сделанное с последнего применения.
+                  if (!window.confirm(t('admin.channels.restoreConfirm'))) return
+                  restoreMutation.mutate()
+                }}
+              >
+                <Undo2 className="h-4 w-4" /> {t('admin.channels.restore')}
+              </Button>
+            )}
+            <Button size="sm" disabled={applyMutation.isPending} onClick={() => setApplyOpen(true)}>
+              <Send className="h-4 w-4" /> {t('admin.channels.apply')}
+            </Button>
+          </div>
         </div>
       )}