refactor(download): 重构下载系统，支持暂停/恢复/取消，修复歌词加载

- 新建 DownloadManager 类（主进程），每个任务独立 AbortController 控制
- 新建 Pinia useDownloadStore 作为渲染进程单一数据源
- 支持暂停/恢复/取消下载，支持断点续传（Range header）
- 批量下载全部完成后发送汇总系统通知，单首不重复通知
- 并发数可配置（1-5），队列持久化（重启后恢复）
- 修复下载列表不全、封面加载失败、通知重复等 bug
- 修复本地/下载歌曲歌词加载：优先从 ID3/FLAC 元数据提取，API 作为 fallback
- 删除 useDownloadStatus.ts，统一状态管理
- DownloadDrawer/DownloadPage 全面重写，移除 @apply 违规
- 新增 5 语言 i18n 键值（暂停/恢复/取消/排队中等）

src/renderer/components/common/DownloadDrawer.vue

@@ -1,9 +1,13 @@
 <template>
-  <div class="download-drawer-trigger">
+  <div class="fixed left-6 bottom-24 z-[999]">
     <n-badge :value="downloadingCount" :max="99" :show="downloadingCount > 0">
-      <n-button circle @click="navigateToDownloads">
+      <n-button
+        circle
+        class="bg-white/80 dark:bg-gray-800/80 shadow-lg backdrop-blur-sm hover:bg-light dark:hover:bg-dark-200 text-gray-600 dark:text-gray-300 transition-all duration-300 w-10 h-10"
+        @click="navigateToDownloads"
+      >
         <template #icon>
-          <i class="iconfont ri-download-cloud-2-line"></i>
+          <i class="iconfont ri-download-cloud-2-line text-xl"></i>
         </template>
       </n-button>
     </n-badge>
@@ -11,102 +15,22 @@
 </template>
 
 <script setup lang="ts">
-import { computed, onMounted, ref } from 'vue';
+import { computed, onMounted } from 'vue';
 import { useRouter } from 'vue-router';
 
+import { useDownloadStore } from '@/store/modules/download';
+
 const router = useRouter();
-const downloadList = ref<any[]>([]);
+const downloadStore = useDownloadStore();
 
-// 计算下载中的任务数量
-const downloadingCount = computed(() => {
-  return downloadList.value.filter((item) => item.status === 'downloading').length;
-});
+const downloadingCount = computed(() => downloadStore.downloadingCount);
 
-// 导航到下载页面
 const navigateToDownloads = () => {
   router.push('/downloads');
 };
 
-// 监听下载进度
 onMounted(() => {
-  // 监听下载进度
-  window.electron.ipcRenderer.on('music-download-progress', (_, data) => {
-    const existingItem = downloadList.value.find((item) => item.filename === data.filename);
-
-    // 如果进度为100%，将状态设置为已完成
-    if (data.progress === 100) {
-      data.status = 'completed';
-    }
-
-    if (existingItem) {
-      Object.assign(existingItem, {
-        ...data,
-        songInfo: data.songInfo || existingItem.songInfo
-      });
-
-      // 如果下载完成，从列表中移除
-      if (data.status === 'completed') {
-        downloadList.value = downloadList.value.filter((item) => item.filename !== data.filename);
-      }
-    } else {
-      downloadList.value.push({
-        ...data,
-        songInfo: data.songInfo
-      });
-    }
-  });
-
-  // 监听下载完成
-  window.electron.ipcRenderer.on('music-download-complete', async (_, data) => {
-    if (data.success) {
-      downloadList.value = downloadList.value.filter((item) => item.filename !== data.filename);
-    } else {
-      const existingItem = downloadList.value.find((item) => item.filename === data.filename);
-      if (existingItem) {
-        Object.assign(existingItem, {
-          status: 'error',
-          error: data.error,
-          progress: 0
-        });
-        setTimeout(() => {
-          downloadList.value = downloadList.value.filter((item) => item.filename !== data.filename);
-        }, 3000);
-      }
-    }
-  });
-
-  // 监听下载队列
-  window.electron.ipcRenderer.on('music-download-queued', (_, data) => {
-    const existingItem = downloadList.value.find((item) => item.filename === data.filename);
-    if (!existingItem) {
-      downloadList.value.push({
-        filename: data.filename,
-        progress: 0,
-        loaded: 0,
-        total: 0,
-        path: '',
-        status: 'downloading',
-        songInfo: data.songInfo
-      });
-    }
-  });
+  downloadStore.initListeners();
+  downloadStore.loadPersistedQueue();
 });
 </script>
-
-<style lang="scss" scoped>
-.download-drawer-trigger {
-  @apply fixed left-6 bottom-24 z-[999];
-
-  .n-button {
-    @apply bg-white/80 dark:bg-gray-800/80 shadow-lg backdrop-blur-sm;
-    @apply hover:bg-light dark:hover:bg-dark-200;
-    @apply text-gray-600 dark:text-gray-300;
-    @apply transition-all duration-300;
-    @apply w-10 h-10;
-
-    .iconfont {
-      @apply text-xl;
-    }
-  }
-}
-</style>