feat: add invite code system and multi-image Drone pipeline

- Add InviteCode model with code, maxUses, expiry, usage tracking
- Registration now requires a valid invite code
- New users get USER role instead of ADMIN
- Admin-only /invites page to create, manage, and share invite codes
- Invite links auto-fill code via ?code= URL param
- Drone pipeline now builds app, worker, and bot images separately
- Add NEXT_PUBLIC_APP_URL build arg to fix URL redirects

src/app/(app)/invites/page.tsx

@@ -0,0 +1,26 @@
+import { auth } from "@/lib/auth";
+import { redirect } from "next/navigation";
+import { PageHeader } from "@/components/shared/page-header";
+import { getInviteCodes } from "./actions";
+import { InviteManager } from "./_components/invite-manager";
+
+export default async function InvitesPage() {
+  const session = await auth();
+  if (!session?.user?.id) redirect("/login");
+  if (session.user.role !== "ADMIN") redirect("/dashboard");
+
+  const inviteCodes = await getInviteCodes();
+
+  return (
+    <div className="space-y-6">
+      <PageHeader
+        title="Invite Codes"
+        description="Manage invite codes for new user registration"
+      />
+      <InviteManager
+        inviteCodes={JSON.parse(JSON.stringify(inviteCodes))}
+        appUrl={process.env.NEXT_PUBLIC_APP_URL ?? ""}
+      />
+    </div>
+  );
+}