Adding login admin, fix ipv6 Vienamese version, add env example

app/api/auth/logout/route.ts

@@ -0,0 +1,13 @@
+import { NextResponse } from "next/server";
+
+export async function POST() {
+  const response = NextResponse.json({ success: true });
+  
+  // Xóa cookie bằng cách set maxAge = 0
+  response.cookies.set("admin_session", "", {
+    path: "/",
+    maxAge: 0,
+  });
+
+  return response;
+}