feat(admin-frontend): 重做登录回跳与仪表盘样式

重构管理端登录、主布局和仪表盘，统一为 Apple 风格
并移除高成本装饰层以提升页面流畅度。

补充仪表盘统计、趋势、排行和系统状态接口封装，
同时完善受保护路由的 redirect 回跳逻辑。

admin-frontend/src/api/admin.ts

@@ -1,8 +1,55 @@
 import { adminClient } from './client'
-import type { ApiResponse, SystemStatus } from '@/types/api'
+import type {
+  ApiResponse,
+  DashboardStats,
+  OrderTrendData,
+  QueueStats,
+  SystemStatus,
+  TrafficRankResponse,
+} from '@/types/api'
 
-export function getSystemStatus(): Promise<ApiResponse<SystemStatus>> {
+function unwrap<T>(url: string, params?: Record<string, unknown>): Promise<ApiResponse<T>> {
   return adminClient
-    .get<ApiResponse<SystemStatus>>('/system/getSystemStatus')
+    .get<ApiResponse<T>>(url, { params })
     .then((res) => res.data)
 }
+
+export function getDashboardStats(): Promise<ApiResponse<DashboardStats>> {
+  return unwrap<DashboardStats>('/stat/getStats')
+}
+
+export function getOrderTrend(params: {
+  startDate: string
+  endDate: string
+  type?: 'paid_total' | 'paid_count' | 'commission_total' | 'commission_count'
+}): Promise<ApiResponse<OrderTrendData>> {
+  return unwrap<OrderTrendData>('/stat/getOrder', {
+    start_date: params.startDate,
+    end_date: params.endDate,
+    type: params.type,
+  })
+}
+
+export function getTrafficRank(params: {
+  type: 'node' | 'user'
+  startTime: number
+  endTime: number
+}): Promise<TrafficRankResponse> {
+  return adminClient
+    .get<TrafficRankResponse>('/stat/getTrafficRank', {
+      params: {
+        type: params.type,
+        start_time: params.startTime,
+        end_time: params.endTime,
+      },
+    })
+    .then((res) => res.data)
+}
+
+export function getSystemStatus(): Promise<ApiResponse<SystemStatus>> {
+  return unwrap<SystemStatus>('/system/getSystemStatus')
+}
+
+export function getQueueStats(): Promise<ApiResponse<QueueStats>> {
+  return unwrap<QueueStats>('/system/getQueueStats')
+}