fix: 多选同步弹窗复用站点同步表单缓存

- 抽取站点地址与 Token 的 24 小时缓存工具
- 存储页与多选同步弹窗共用 pichost.site-sync-form
- 弹窗打开时读取最新缓存，修改后写回
- 增加缓存读取与过期测试

app/components/storage/SiteSyncCard.vue

@@ -3,6 +3,7 @@ import type {
   SiteSyncDirection,
   SiteSyncRequest
 } from '~/types/backup'
+import { loadSiteSyncForm, saveSiteSyncForm } from '~/utils/site-sync-form'
 
 const props = defineProps<{
   busy: boolean
@@ -30,42 +31,15 @@ const conflictMode = ref<'skip' | 'overwrite'>('skip')
 const direction = ref<SiteSyncDirection>('push')
 const scope = ref<'all' | 'image' | 'video' | 'file'>('all')
 
-/** 目标站点地址与 Token 自动保存 24 小时 */
-const FORM_STORAGE_KEY = 'pichost.site-sync-form'
-const FORM_TTL_MS = 24 * 60 * 60 * 1000
-
 function loadSavedForm() {
   if (!import.meta.client) return
-  try {
-    const raw = localStorage.getItem(FORM_STORAGE_KEY)
-    if (!raw) return
-    const data = JSON.parse(raw) as {
-      targetBaseUrl?: string
-      token?: string
-      savedAt?: number
-    }
-    if (!data.savedAt || Date.now() - data.savedAt > FORM_TTL_MS) {
-      localStorage.removeItem(FORM_STORAGE_KEY)
-      return
-    }
-    if (data.targetBaseUrl) targetBaseUrl.value = data.targetBaseUrl
-    if (data.token) token.value = data.token
-  } catch {
-    localStorage.removeItem(FORM_STORAGE_KEY)
-  }
+  const saved = loadSiteSyncForm()
+  if (saved?.targetBaseUrl) targetBaseUrl.value = saved.targetBaseUrl
+  if (saved?.token) token.value = saved.token
 }
 
 function persistForm() {
-  if (!import.meta.client) return
-  try {
-    localStorage.setItem(FORM_STORAGE_KEY, JSON.stringify({
-      targetBaseUrl: targetBaseUrl.value,
-      token: token.value,
-      savedAt: Date.now()
-    }))
-  } catch {
-    // 存储不可用时忽略
-  }
+  saveSiteSyncForm(targetBaseUrl.value, token.value)
 }
 
 watch([targetBaseUrl, token], persistForm)