Refactor group deletion logic to handle fallback group references

Updated the DeleteGroupCommandHandler to release fallback group references during group deletion, ensuring that groups can be removed even when used as fallback in templates. Adjusted related tests to verify the correct behavior of the deletion process, confirming that fallback references are cleared appropriately. Enhanced localization strings to provide clearer context for fallback group functionality in both English and Russian.

frontend/src/features/admin/channels/components/RulesCard.tsx

@@ -1,7 +1,9 @@
-import { useMutation } from '@tanstack/react-query'
+import { useMutation, useQuery } from '@tanstack/react-query'
 import { Plus, Trash2 } from 'lucide-react'
 import { useEffect, useState } from 'react'
 import { useTranslation } from 'react-i18next'
+import { listGroups } from '@/features/admin/groups/api'
+import { qk } from '@/shared/api/query-keys'
 import {
   SHOW_AUDIENCES,
   type AudienceWindow,
@@ -55,6 +57,11 @@ export function RulesCard({
   const [breakCap, setBreakCap] = useState(() => template.rules?.maxBreakMinutesPerHour ?? 0)
   const [genreCap, setGenreCap] = useState(() => template.rules?.maxGenreSharePercent ?? 0)
   const [fallbackCap, setFallbackCap] = useState(() => template.rules?.maxFallbackSharePercent ?? 0)
+  const [fallbackGroupId, setFallbackGroupId] = useState(() => template.fallbackGroupId)
+
+  // Аварийную группу проставляет и автосборка сетки, поэтому список нужен всегда: без него
+  // ссылка остаётся невидимой, а снять её нечем — и группа не удаляется.
+  const { data: groups } = useQuery({ queryKey: qk.groups.all, queryFn: listGroups })
 
   useEffect(() => {
     setWindows(toRows(template.rules?.maxAudienceByTime ?? []))
@@ -64,6 +71,7 @@ export function RulesCard({
     setBreakCap(template.rules?.maxBreakMinutesPerHour ?? 0)
     setGenreCap(template.rules?.maxGenreSharePercent ?? 0)
     setFallbackCap(template.rules?.maxFallbackSharePercent ?? 0)
+    setFallbackGroupId(template.fallbackGroupId)
   }, [template])
 
   const save = useMutation({
@@ -78,7 +86,7 @@ export function RulesCard({
       }
       return updateTemplate(template.id, {
         name: template.name,
-        fallbackGroupId: template.fallbackGroupId,
+        fallbackGroupId,
         defaultJunctionId: template.defaultJunctionId,
         rules,
       })
@@ -203,6 +211,25 @@ export function RulesCard({
           <p className="text-xs text-muted-foreground">{t('admin.channels.repeatLimitHint')}</p>
         </div>
 
+        <div className="flex flex-col gap-2 border-t border-border pt-4">
+          <div className="flex flex-col gap-1.5">
+            <Label>{t('admin.channels.fallbackGroup')}</Label>
+            <select
+              className="h-9 rounded-md border border-border bg-transparent px-2"
+              value={fallbackGroupId ?? ''}
+              onChange={(e) => setFallbackGroupId(e.target.value || null)}
+            >
+              <option value="">{t('admin.channels.fallbackGroupNone')}</option>
+              {(groups ?? []).map((group) => (
+                <option key={group.id} value={group.id}>
+                  {group.name} · {group.itemCount}
+                </option>
+              ))}
+            </select>
+          </div>
+          <p className="text-xs text-muted-foreground">{t('admin.channels.fallbackGroupHint')}</p>
+        </div>
+
         <div className="flex flex-col gap-2 border-t border-border pt-4">
           <h3 className="text-xs font-semibold uppercase tracking-wide text-muted-foreground">
             {t('admin.channels.postChecks')}