fix: resolve backend docker build errors

apps/backend/src/plugins/auth.ts

@@ -1,6 +1,7 @@
 import fp from 'fastify-plugin';
 import fastifyJwt from '@fastify/jwt';
 import fastifyCookie from '@fastify/cookie';
+import type { FastifyReply } from 'fastify';
 import { env } from '../config/env.js';
 import { UnauthorizedError } from '../utils/errors.js';
 
@@ -28,7 +29,7 @@ export default fp(async (app) => {
   });
 
   // helpers for routes
-  app.decorate('setAuthCookie', ((reply, token) => {
+  app.decorate('setAuthCookie', ((reply: FastifyReply, token: string) => {
     reply.setCookie(AUTH_COOKIE, token, {
       httpOnly: true,
       secure: env.NODE_ENV === 'production',
@@ -38,7 +39,7 @@ export default fp(async (app) => {
     });
   }) as never);
 
-  app.decorate('clearAuthCookie', ((reply) => {
+  app.decorate('clearAuthCookie', ((reply: FastifyReply) => {
     reply.clearCookie(AUTH_COOKIE, { path: '/' });
   }) as never);
 });