fix: remove dead localStorage writes and hardcoded key

- Remove unused `dns_settings_enabled` localStorage writes in
  setting-clash.tsx — state is sourced from verge config, these
  writes were never read anywhere.
- Replace hardcoded `'last_check_update'` localStorage read in
  system-info-card.tsx with exported `readLastCheckTime()` from
  the useUpdate hook, keeping the key in a single source of truth.

src/components/home/system-info-card.tsx

@@ -13,7 +13,11 @@ import { useNavigate } from 'react-router'
 
 import { useServiceInstaller } from '@/hooks/use-service-installer'
 import { useSystemState } from '@/hooks/use-system-state'
-import { useUpdate, updateLastCheckTime } from '@/hooks/use-update'
+import {
+  useUpdate,
+  updateLastCheckTime,
+  readLastCheckTime,
+} from '@/hooks/use-update'
 import { useVerge } from '@/hooks/use-verge'
 import { getSystemInfo } from '@/services/cmds'
 import { showNotice } from '@/services/notice-service'
@@ -63,8 +67,7 @@ export const SystemInfoCard = () => {
   // 如果启用了自动检查更新但没有记录，设置当前时间并延迟检查
   useEffect(() => {
     if (!verge?.auto_check_update) return
-    const stored = localStorage.getItem('last_check_update')
-    if (stored) return
+    if (readLastCheckTime() !== null) return
 
     updateLastCheckTime()
     const timeoutId = window.setTimeout(() => {

src/components/setting/setting-clash.tsx

@@ -78,7 +78,6 @@ const SettingClash = ({ onError }: Props) => {
   const handleDnsToggle = useLockFn(async (enable: boolean) => {
     try {
       setDnsSettingsEnabled(enable)
-      localStorage.setItem('dns_settings_enabled', String(enable))
       await patchVerge({ enable_dns_settings: enable })
       await invoke('apply_dns_config', { apply: enable })
       setTimeout(() => {
@@ -86,7 +85,6 @@ const SettingClash = ({ onError }: Props) => {
       }, 500)
     } catch (err: any) {
       setDnsSettingsEnabled(!enable)
-      localStorage.setItem('dns_settings_enabled', String(!enable))
       showNotice.error(err)
       await patchVerge({ enable_dns_settings: !enable }).catch(() => {})
       throw err

src/hooks/use-update.ts

@@ -16,7 +16,7 @@ export interface UpdateInfo {
 
 const LAST_CHECK_KEY = 'last_check_update'
 
-const readLastCheckFromStorage = (): number | null => {
+export const readLastCheckTime = (): number | null => {
   const stored = localStorage.getItem(LAST_CHECK_KEY)
   if (!stored) return null
   const ts = parseInt(stored, 10)
@@ -63,14 +63,10 @@ export const useUpdate = (
   })
 
   // Shared last check timestamp
-  const { data: lastCheckUpdate } = useSWR(
-    LAST_CHECK_KEY,
-    readLastCheckFromStorage,
-    {
-      revalidateOnFocus: false,
-      revalidateOnReconnect: false,
-    },
-  )
+  const { data: lastCheckUpdate } = useSWR(LAST_CHECK_KEY, readLastCheckTime, {
+    revalidateOnFocus: false,
+    revalidateOnReconnect: false,
+  })
 
   return {
     updateInfo,