feat: 离线License批量删除；同步循环加固（启动即跑/pending自动握手/防重入/panic恢复，移至main启动）；同步时间显示到秒

frontend/src/views/OfflineLicenses.vue

@@ -9,6 +9,9 @@
           </el-select>
         </div>
         <div>
+          <el-button type="danger" plain :disabled="!selectedRows.length" @click="batchDelete">
+            批量删除{{ selectedRows.length ? `（${selectedRows.length}）` : '' }}
+          </el-button>
           <el-button type="primary" @click="openIssue">签发离线序列号</el-button>
         </div>
       </div>
@@ -21,7 +24,8 @@
         style="margin-bottom: 12px"
       />
 
-      <el-table :data="list" v-loading="loading" stripe>
+      <el-table :data="list" v-loading="loading" stripe @selection-change="onSelectionChange">
+        <el-table-column type="selection" width="48" />
         <el-table-column label="序列号" min-width="200">
           <template #default="{ row }">
             <div class="serial-cell">
@@ -112,9 +116,35 @@
 <script setup>
 import { ref, reactive, computed, onMounted } from 'vue'
 import { ElMessage, ElMessageBox } from 'element-plus'
-import { getLicenses, issueOfflineLicense, revokeLicense } from '@/api/license'
+import { getLicenses, issueOfflineLicense, revokeLicense, batchDeleteLicenses } from '@/api/license'
 
 const list = ref([])
+const selectedRows = ref([])
+
+// 仅已吊销 / 已过期可删除（与在线 License 一致） // Logan.Li
+function canDelete(row) {
+  return row.status === 'revoked' || row.status === 'expired' || row.days_left <= 0
+}
+
+function onSelectionChange(rows) {
+  selectedRows.value = rows || []
+}
+
+async function batchDelete() {
+  const ids = selectedRows.value.map((r) => r.id).filter(Boolean)
+  if (!ids.length) return
+  const deletable = selectedRows.value.filter(canDelete).length
+  await ElMessageBox.confirm(
+    `已选 ${ids.length} 条，其中约 ${deletable} 条可删（仅已吊销/已过期）；其余将跳过。确认继续？`,
+    '批量删除',
+    { type: 'warning' },
+  )
+  const res = await batchDeleteLicenses(ids)
+  const data = res.data || {}
+  ElMessage.success(`删除 ${data.deleted || 0} 条，跳过 ${data.skipped || 0} 条${data.failed ? `，失败 ${data.failed}` : ''}`)
+  selectedRows.value = []
+  loadData()
+}
 const loading = ref(false)
 const keyword = ref('')
 const statusFilter = ref('')

frontend/src/views/Sync.vue

@@ -22,7 +22,9 @@
         <el-table-column label="密钥尾号" width="90">
           <template #default="{ row }"><code>…{{ row.key_tail }}</code></template>
         </el-table-column>
-        <el-table-column prop="last_sync_at" label="上次同步" width="160" />
+        <el-table-column label="上次同步" width="160">
+          <template #default="{ row }">{{ formatTime(row.last_sync_at) }}</template>
+        </el-table-column>
         <el-table-column prop="last_result" label="最近结果" min-width="200" show-overflow-tooltip />
         <el-table-column label="操作" width="240" fixed="right">
           <template #default="{ row }">
@@ -129,6 +131,15 @@ async function doDelete(row) {
   await load()
 }
 
+// formatTime 时间展示精确到秒（后端返回带纳秒的 RFC3339） // Logan.Li
+function formatTime(v) {
+  if (!v) return '—'
+  const d = new Date(v)
+  if (Number.isNaN(d.getTime())) return v
+  const p = (n) => String(n).padStart(2, '0')
+  return `${d.getFullYear()}-${p(d.getMonth() + 1)}-${p(d.getDate())} ${p(d.getHours())}:${p(d.getMinutes())}:${p(d.getSeconds())}`
+}
+
 onMounted(load)
 </script>