feat(M05-B): 完成微信支付退款与对账基础

backend/src/app.ts

@@ -58,6 +58,7 @@ export interface BuildAppOptions {
 declare module 'fastify' {
   interface FastifyRequest {
     traceId: string;
+    rawBody: string;
   }
 }
 
@@ -71,6 +72,7 @@ export async function buildApp(options: BuildAppOptions = {}): Promise<FastifyIn
   });
 
   app.decorateRequest('traceId', '');
+  app.decorateRequest('rawBody', '');
   app.addHook('onRequest', async (request, reply) => {
     const traceHeader = request.headers['x-trace-id'];
     request.traceId = Array.isArray(traceHeader) ? traceHeader[0] : traceHeader || request.id;