feat(frontend): 分页 pageSize 持久化到 localStorage，刷新后自动恢复

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/views/user/KeysView.vue

@@ -1035,6 +1035,7 @@
 	import { useAppStore } from '@/stores/app'
 	import { useOnboardingStore } from '@/stores/onboarding'
 	import { useClipboard } from '@/composables/useClipboard'
+import { getPersistedPageSize } from '@/composables/usePersistedPageSize'
 
 const { t } = useI18n()
 import { keysAPI, authAPI, usageAPI, userGroupsAPI } from '@/api'
@@ -1101,7 +1102,7 @@ const userGroupRates = ref<Record<number, number>>({})
 
 const pagination = ref({
   page: 1,
-  page_size: 10,
+  page_size: getPersistedPageSize(),
   total: 0,
   pages: 0
 })