chore: 提交所有工作进度 — SaaS 后端增强、Admin UI、桌面端集成

包含大量 SaaS 平台改进、Admin 管理后台更新、桌面端集成完善、
文档同步、测试文件重构等内容。为 QA 测试准备干净工作树。

admin/src/components/ui/state.tsx

@@ -0,0 +1,63 @@
+'use client'
+
+import { AlertCircle, Inbox } from 'lucide-react'
+
+/** 统一的错误提示横幅 */
+export function ErrorBanner({
+  message,
+  onDismiss,
+}: {
+  message: string
+  onDismiss?: () => void
+}) {
+  return (
+    <div className="rounded-md bg-destructive/10 border border-destructive/20 px-4 py-3 text-sm text-destructive flex items-center gap-2">
+      <AlertCircle className="h-4 w-4 shrink-0" />
+      <span className="flex-1">{message}</span>
+      {onDismiss && (
+        <button
+          onClick={onDismiss}
+          className="underline cursor-pointer shrink-0"
+        >
+          关闭
+        </button>
+      )}
+    </div>
+  )
+}
+
+/** 统一的空状态占位 */
+export function EmptyState({
+  message = '暂无数据',
+}: {
+  message?: string
+}) {
+  return (
+    <div className="flex h-64 flex-col items-center justify-center gap-2 text-muted-foreground">
+      <Inbox className="h-8 w-8" />
+      <span className="text-sm">{message}</span>
+    </div>
+  )
+}
+
+/** 统一的加载失败提示 + 重试 */
+export function ErrorRetry({
+  message = '请求失败，请重试',
+  onRetry,
+}: {
+  message?: string
+  onRetry: () => void
+}) {
+  return (
+    <div className="flex h-64 flex-col items-center justify-center gap-3 text-muted-foreground">
+      <AlertCircle className="h-8 w-8 text-destructive" />
+      <span className="text-sm">{message}</span>
+      <button
+        onClick={onRetry}
+        className="rounded-md bg-primary px-4 py-2 text-sm text-primary-foreground hover:bg-primary/90 transition-colors cursor-pointer"
+      >
+        重新加载
+      </button>
+    </div>
+  )
+}