feat(exc): 专长交易 read-only monitoring pages

New nav group with four pages against the Exc admin API:
- /exc/demands — status/mode filters, detail sheet with related
  services, quotes and dispatch rounds
- /exc/dispatches — status/round filters
- /exc/orders — status/payment filters, detail sheet with items and
  状态流转 audit trail
- /exc/providers — status/verified filters, detail sheet with dispatch
  settings and status logs

Co-Authored-By: Claude Fable 5 <[email protected]>

src/api/modules/exc.ts

@@ -0,0 +1,40 @@
+import { api } from '@/api/client'
+import type {
+  ApiResponse,
+  ExcDemand,
+  ExcDispatch,
+  ExcOrder,
+  ExcProvider,
+  ListParams,
+  PaginatedResponse,
+} from '@/api/types'
+
+const BASE = '/api/admin/v1/exc'
+
+export function fetchExcDemands(params: ListParams) {
+  return api.get<PaginatedResponse<ExcDemand>>(`${BASE}/demands`, params)
+}
+
+export function fetchExcDemand(id: number) {
+  return api.get<ApiResponse<ExcDemand>>(`${BASE}/demands/${id}`)
+}
+
+export function fetchExcDispatches(params: ListParams) {
+  return api.get<PaginatedResponse<ExcDispatch>>(`${BASE}/dispatches`, params)
+}
+
+export function fetchExcOrders(params: ListParams) {
+  return api.get<PaginatedResponse<ExcOrder>>(`${BASE}/orders`, params)
+}
+
+export function fetchExcOrder(id: number) {
+  return api.get<ApiResponse<ExcOrder>>(`${BASE}/orders/${id}`)
+}
+
+export function fetchExcProviders(params: ListParams) {
+  return api.get<PaginatedResponse<ExcProvider>>(`${BASE}/providers`, params)
+}
+
+export function fetchExcProvider(uid: string) {
+  return api.get<ApiResponse<ExcProvider>>(`${BASE}/providers/${uid}`)
+}