chore(config): centralize feature settings

app/privacy/page.tsx

@@ -1,5 +1,6 @@
 import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
 import { Separator } from "@/components/ui/separator";
+import { config } from "@/lib/config";
 import Link from "next/link";
 import { Button } from "@/components/ui/button";
 import { ArrowLeft } from "lucide-react";
@@ -99,7 +100,7 @@ export default function PrivacyPolicyPage() {
           <CardContent className="text-sm text-muted-foreground leading-relaxed">
             หากมีคำถามเกี่ยวกับนโยบายความเป็นส่วนตัว สามารถติดต่อได้ผ่านทาง{" "}
             <a
-              href="https://discord.com/invite/3cZQbvW6cF"
+              href={config.site.discordInviteUrl}
               target="_blank"
               rel="noopener noreferrer"
               className="underline text-foreground hover:text-primary"