refactor: rename middleware.ts to proxy.ts per Next.js 16 spec

shop/proxy.ts

@@ -1,7 +1,7 @@
 import { updateSession } from "@/lib/supabase/proxy";
 import { type NextRequest } from "next/server";
 
-export async function middleware(request: NextRequest) {
+export async function proxy(request: NextRequest) {
   return await updateSession(request);
 }