feat: paginate dashboard clients and proxies via API v2 (#5354)

Move the frps dashboard Clients and Proxies views to the paginated
/api/v2/clients and /api/v2/proxies endpoints instead of fetching all
data at once, and extend server-side proxy search so the search box
keeps working under pagination.

Frontend:
- Add V2Envelope/V2Page types and getV2 HTTP helper to api/http.ts
- Add v2 paginated fetch functions to api/client.ts and api/proxy.ts
- Add ClientV2Info and ProxyV2Info types for v2 API responses
- Rewrite Clients.vue with server-side pagination, status/user search
  filtering, and ElPagination component
- Rewrite Proxies.vue with server-side pagination, type tabs, client
  dropdown filter, and a search box that passes q to the API
- Default page size 10, selectable sizes [10, 20, 50, 100]

Backend:
- Extend /api/v2/proxies q matching to also cover online proxy spec
  fields: TCP/UDP remotePort and HTTP/HTTPS/TCPMux customDomains and
  subdomain, so dashboard search no longer needs to scan every page
- Add controller_v2 tests for the new spec-field matching

web/frps/src/api/http.ts

@@ -11,6 +11,21 @@ class HTTPError extends Error {
   }
 }
 
+export interface V2Envelope<T> {
+  code: number
+  msg: string
+  data: T
+}
+
+export interface V2Page<T> {
+  total: number
+  page: number
+  pageSize: number
+  items: T[]
+}
+
+type QueryParamValue = string | number | boolean | null | undefined
+
 async function request<T>(url: string, options: RequestInit = {}): Promise<T> {
   const defaultOptions: RequestInit = {
     credentials: 'include',
@@ -34,9 +49,55 @@ async function request<T>(url: string, options: RequestInit = {}): Promise<T> {
   return response.json()
 }
 
+async function requestV2<T>(
+  url: string,
+  options: RequestInit = {},
+): Promise<T> {
+  const defaultOptions: RequestInit = {
+    credentials: 'include',
+  }
+
+  const response = await fetch(url, { ...defaultOptions, ...options })
+  const envelope = (await response.json().catch(() => null)) as
+    | V2Envelope<T>
+    | null
+
+  if (!response.ok) {
+    throw new HTTPError(
+      response.status,
+      response.statusText,
+      envelope?.msg || `HTTP ${response.status}`,
+    )
+  }
+
+  if (!envelope || typeof envelope.code !== 'number') {
+    throw new Error('Invalid API v2 response')
+  }
+
+  if (envelope.code >= 400) {
+    throw new HTTPError(envelope.code, envelope.msg, envelope.msg)
+  }
+
+  return envelope.data
+}
+
+export const buildQueryString = (
+  params: Record<string, QueryParamValue>,
+): string => {
+  const query = new URLSearchParams()
+  for (const [key, value] of Object.entries(params)) {
+    if (value === null || value === undefined) continue
+    query.append(key, String(value))
+  }
+  const text = query.toString()
+  return text ? `?${text}` : ''
+}
+
 export const http = {
   get: <T>(url: string, options?: RequestInit) =>
     request<T>(url, { ...options, method: 'GET' }),
+  getV2: <T>(url: string, options?: RequestInit) =>
+    requestV2<T>(url, { ...options, method: 'GET' }),
   post: <T>(url: string, body?: any, options?: RequestInit) =>
     request<T>(url, {
       ...options,