refactor: change to default export

As the class is the only export in that module, it's better to have it
as a default export.

Author: pheuberger

src/controllers/SignatureRequestController.ts

@@ -11,7 +11,7 @@ import {
 
 import { SupabaseDataService } from "../services/SupabaseDataService.js";
 import { verifyAuthSignedData } from "../utils/verifyAuthSignedData.js";
-import { SignatureRequestProcessor } from "../services/SignatureRequestProcessor.js";
+import SignatureRequestProcessor from "../services/SignatureRequestProcessor.js";
 
 interface CancelSignatureRequest {
   signature: string;

src/services/SignatureRequestProcessor.ts

@@ -8,7 +8,7 @@ import { SafeApiQueue } from "./SafeApiQueue.js";
 type SignatureRequest =
   Database["public"]["Tables"]["signature_requests"]["Row"];
 
-export class SignatureRequestProcessor {
+export default class SignatureRequestProcessor {
   private static instance: SignatureRequestProcessor;
 
   private readonly dataService: SupabaseDataService;