feat(quota): add downloadable traffic quota with local/OSS/share metering

backend/auth.js

@@ -175,6 +175,17 @@ function authMiddleware(req, res, next) {
     const effectiveOssQuota = Number.isFinite(rawOssQuota) && rawOssQuota > 0
       ? rawOssQuota
       : DEFAULT_OSS_STORAGE_QUOTA_BYTES;
+    const rawDownloadTrafficQuota = Number(user.download_traffic_quota);
+    const effectiveDownloadTrafficQuota = Number.isFinite(rawDownloadTrafficQuota) && rawDownloadTrafficQuota > 0
+      ? Math.floor(rawDownloadTrafficQuota)
+      : 0; // 0 表示不限流量
+    const rawDownloadTrafficUsed = Number(user.download_traffic_used);
+    const normalizedDownloadTrafficUsed = Number.isFinite(rawDownloadTrafficUsed) && rawDownloadTrafficUsed > 0
+      ? Math.floor(rawDownloadTrafficUsed)
+      : 0;
+    const cappedDownloadTrafficUsed = effectiveDownloadTrafficQuota > 0
+      ? Math.min(normalizedDownloadTrafficUsed, effectiveDownloadTrafficQuota)
+      : normalizedDownloadTrafficUsed;
 
     // 将用户信息附加到请求对象（包含所有存储相关字段）
     req.user = {
@@ -198,6 +209,8 @@ function authMiddleware(req, res, next) {
       local_storage_used: user.local_storage_used || 0,
       oss_storage_quota: effectiveOssQuota,
       storage_used: user.storage_used || 0,
+      download_traffic_quota: effectiveDownloadTrafficQuota,
+      download_traffic_used: cappedDownloadTrafficUsed,
       // 主题偏好
       theme_preference: user.theme_preference || null
     };