fix: revert proxy back to middleware for Next.js build compatibility

src/middleware.ts

@@ -1,7 +1,7 @@
 import { NextResponse } from "next/server";
 import type { NextRequest } from "next/server";
 
-export function proxy(request: NextRequest) {
+export function middleware(request: NextRequest) {
   const response = NextResponse.next();
 
   const url = request.nextUrl.pathname;