fix: 优化 VOD API 错误提示，显示具体错误信息

apps/macos/VODManager/Sources/VODManager/Services/VODClient.swift

@@ -1,10 +1,23 @@
 import Foundation
 
-enum VODClientError: Error {
+enum VODClientError: Error, LocalizedError {
     case noActiveAccount
     case invalidResponse
     case apiError(String)
     case networkError(Error)
+
+    var errorDescription: String? {
+        switch self {
+        case .noActiveAccount:
+            return "没有激活的阿里云账号，请先在「账号配置」中添加并切换账号"
+        case .invalidResponse:
+            return "无法解析服务器响应"
+        case .apiError(let message):
+            return "阿里云 API 错误：\(message)"
+        case .networkError(let underlying):
+            return "网络错误：\(underlying.localizedDescription)"
+        }
+    }
 }
 
 actor VODClient {