feat(billing): implement robust in-app subscription cancellation & fix CI/CD socket port typo

memento-note/app/api/billing/cancel/route.ts

@@ -0,0 +1,30 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { auth } from '@/auth';
+import { cancelSubscription } from '@/lib/billing/cancel-subscription';
+
+export const dynamic = 'force-dynamic';
+
+export async function POST(req: NextRequest) {
+  const session = await auth();
+  if (!session?.user?.id) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+  }
+
+  const userId = session.user.id;
+
+  try {
+    const result = await cancelSubscription(userId);
+    if (!result.success) {
+      const isNotFound = result.error === 'No active subscription found';
+      return NextResponse.json(
+        { error: result.error },
+        { status: isNotFound ? 404 : 400 }
+      );
+    }
+
+    return NextResponse.json({ success: true });
+  } catch (error) {
+    console.error('[billing/cancel] Route handler crash:', error);
+    return NextResponse.json({ error: 'Failed to cancel subscription' }, { status: 500 });
+  }
+}