feat: 全站 PageShell 设计系统与专业 UI 统一

- 新增 PageShell/PageTabs/ContentPanel/PageLoading/PageEmpty 页面骨架
- index.css 设计令牌文档化，布局令牌与纯色主按钮（去除渐变粉彩）
- 全站路由页接入 PageShell，云账单三 Tab 为标杆
- 主题体系：跟随系统 + 主流/开发者分组，新增 Dracula/Tokyo Night，One Dark 暖灰差异化
- 登录页/侧栏/顶栏去渐变光球，企业克制风
- 修复 AIAlertAnalyzer JSX 与构建依赖导入问题

frontend/src/components/approval/ApprovalProcessTab.tsx

@@ -37,17 +37,17 @@ function getStatusBadge(status: string) {
   const statusMap: Record<string, { labelKey: string; className: string; dot: string }> = {
     pending: {
       labelKey: 'approval.status.pending',
-      className: 'border-amber-500/30 text-amber-400 bg-amber-500/10',
+      className: 'border-amber-500/30 dg-text-yellow bg-amber-500/10',
       dot: 'bg-amber-400',
     },
     approved: {
       labelKey: 'approval.status.approved',
-      className: 'border-emerald-500/30 text-emerald-400 bg-emerald-500/10',
+      className: 'border-emerald-500/30 dg-text-green bg-emerald-500/10',
       dot: 'bg-emerald-400',
     },
     rejected: {
       labelKey: 'approval.status.rejected',
-      className: 'border-red-500/30 text-red-400 bg-red-500/10',
+      className: 'border-red-500/30 dg-text-red bg-red-500/10',
       dot: 'bg-red-400',
     },
     processing: {
@@ -186,7 +186,7 @@ export function ApprovalProcessTab({
                           <Button
                             variant="outline"
                             size="sm"
-                            className="border-emerald-500/30 text-emerald-400 hover:bg-emerald-500/10"
+                            className="border-emerald-500/30 dg-text-green hover:bg-emerald-500/10"
                             onClick={() => onApprove(instance)}
                           >
                             <CheckCircle2 className="h-4 w-4 mr-1" />
@@ -195,7 +195,7 @@ export function ApprovalProcessTab({
                           <Button
                             variant="outline"
                             size="sm"
-                            className="border-red-500/30 text-red-400 hover:bg-red-500/10"
+                            className="border-red-500/30 dg-text-red hover:bg-red-500/10"
                             onClick={() => onReject(instance)}
                           >
                             <XCircle className="h-4 w-4 mr-1" />