fix(home): update last check timestamp on manual update check (#6605)

The onCheckUpdate handler never persisted the timestamp to localStorage
or dispatched it to component state, so clicking "Last Check Update"
would report the result but leave the displayed time stale.

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

@@ -157,6 +157,12 @@ export const SystemInfoCard = () => {
   const onCheckUpdate = useLockFn(async () => {
     try {
       const info = await triggerCheckUpdate()
+      const now = Date.now()
+      localStorage.setItem('last_check_update', now.toString())
+      dispatchSystemState({
+        type: 'set-last-check-update',
+        payload: new Date(now).toLocaleString(),
+      })
       if (!info?.available) {
         showNotice.success(
           'settings.components.verge.advanced.notifications.latestVersion',