use an env var for configurable proxy header (#8863)

src/state/queries/service.ts

@@ -1,6 +1,7 @@
-import {BskyAgent} from '@atproto/api'
 import {useQuery} from '@tanstack/react-query'
 
+import {Agent} from '../session/agent'
+
 const RQKEY_ROOT = 'service'
 export const RQKEY = (serviceUrl: string) => [RQKEY_ROOT, serviceUrl]
 
@@ -8,7 +9,7 @@ export function useServiceQuery(serviceUrl: string) {
   return useQuery({
     queryKey: RQKEY(serviceUrl),
     queryFn: async () => {
-      const agent = new BskyAgent({service: serviceUrl})
+      const agent = new Agent(null, {service: serviceUrl})
       const res = await agent.com.atproto.server.describeServer()
       return res.data
     },