fix: 皮肤包删除后被自动迁移逻辑复活，IPA 下载连击刷屏操作日志

_migrate_old_themes 之前每次 load_config() 都会重跑，只要证书仍引用某皮肤
且旧版 themes 目录还在，删除后会被立即重新生成；现改为仅首次执行一次并
在 config.json 中打标记跳过后续调用。

打包历史下载 IPA 按钮此前无连击防护，前端加 in-flight 禁用态，后端对同一
用户同一任务的下载操作日志增加 5 秒去重，避免连击刷屏审计日志。

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/views/HistoryView.vue

@@ -56,7 +56,7 @@
                 <img v-if="task.build_type === 'Ad_Hoc' && task.qr_code_path"
                      :src="task.qr_code_path" alt="QR" class="qr-thumb"
                      @click="showQrPreview(task)">
-                <button v-if="task.build_type === 'App_Store'" class="download-link" @click="downloadIpa(task.id)">下载 IPA</button>
+                <button v-if="task.build_type === 'App_Store'" class="download-link" :disabled="!!downloadingIds[task.id]" @click="downloadIpa(task.id)">{{ downloadingIds[task.id] ? '下载中...' : '下载 IPA' }}</button>
               </template>
               <span v-else class="text-muted">-</span>
             </td>
@@ -159,7 +159,7 @@
 </template>
 
 <script setup>
-import { ref, computed, onMounted, nextTick, onUnmounted, inject } from 'vue'
+import { ref, reactive, computed, onMounted, nextTick, onUnmounted, inject } from 'vue'
 
 const getToken = inject('getToken', () => '')
 const isAdmin = inject('isAdmin', ref(false))
@@ -182,6 +182,7 @@ const logContainer = ref(null)
 const showVerboseLogs = ref(false)
 const qrPreview = ref(null)
 const showSuperseded = ref(false)
+const downloadingIds = reactive({})
 let logWs = null
 
 const getAppVersion = (task) => {
@@ -313,6 +314,8 @@ const downloadDsym = (taskId) => {
 }
 
 const downloadIpa = async (taskId) => {
+  if (downloadingIds[taskId]) return
+  downloadingIds[taskId] = true
   try {
     const res = await authFetch(`/api/tasks/${taskId}/download-link`)
     if (!res.ok) throw new Error()
@@ -320,6 +323,8 @@ const downloadIpa = async (taskId) => {
     window.open(url, '_blank')
   } catch {
     alert('下载失败，请稍后重试')
+  } finally {
+    delete downloadingIds[taskId]
   }
 }
 
@@ -524,6 +529,8 @@ const errorCategoryLabel = (cat) => {
 .btn-close-log:hover { border-color: #1890ff; color: #1890ff; }
 .download-link { color: #1890ff; text-decoration: none; font-size: 13px; border: none; background: none; cursor: pointer; padding: 0; }
 .download-link:hover { text-decoration: underline; }
+.download-link:disabled { color: #999; cursor: default; }
+.download-link:disabled:hover { text-decoration: none; }
 .text-muted { color: #999; font-size: 13px; }
 .qr-thumb { width: 40px; height: 40px; cursor: pointer; border-radius: 4px; border: 1px solid #e8e8e8; }
 .qr-thumb:hover { border-color: #1890ff; }