Fix moderation lists error: import and instantiate RelayBatchFetcher

The NostrClient.fetchListIncrementally() method delegates to
this.relayBatchFetcher, but RelayBatchFetcher was never imported or
instantiated in client.js, causing "Cannot read properties of undefined
(reading 'fetchListIncrementally')" on every page load when admin lists
try to load.

https://claude.ai/code/session_01KuHrohbGvitA41A2fPD5p5

js/nostr/client.js

@@ -42,6 +42,7 @@ import {
   normalizeStoragePointer,
   resolveStoragePointerValue,
 } from "../utils/storagePointer.js";
+import { RelayBatchFetcher } from "./relayBatchFetcher.js";
 import {
   createWatchHistoryManager,
   normalizePointerInput,
@@ -580,6 +581,7 @@ export class NostrClient {
   constructor() {
     this.connectionManager = new ConnectionManager(this);
     this.signerManager = new SignerManager(this);
+    this.relayBatchFetcher = new RelayBatchFetcher(this);
 
     /**
      * @type {Map<string, object>}