feat(billing): integrate Stripe for subscription management and billing access

- Added billing-related fields to the User model in the database.
- Implemented functions for managing billing access, including trial periods and subscription statuses.
- Created new billing utility functions for Stripe integration.
- Updated onboarding page to include billing overview and workspace creation eligibility.
- Enhanced route access checks to require billing access for certain actions.
- Implemented cleanup scripts for expired billing workspaces and associated media.
- Updated header component to conditionally show app navigation based on billing access.
- Added new migrations for billing-related database changes.

app/api/billing/portal/route.ts

@@ -0,0 +1,55 @@
+import { NextRequest } from 'next/server';
+import { auth } from '@/lib/auth';
+import { apiErrors, successResponse, withCacheControl } from '@/lib/api-response';
+import { getBillingOverview } from '@/lib/billing';
+import { rateLimit } from '@/lib/rate-limit';
+import { getStripe, isStripeConfigured } from '@/lib/stripe';
+import { isTrustedSameOriginRequest } from '@/lib/request-origin';
+
+function getAppOrigin(request: NextRequest) {
+  if (isTrustedSameOriginRequest(request)) {
+    const origin = request.headers.get('origin');
+    if (origin) {
+      return new URL(origin).origin;
+    }
+  }
+
+  return request.nextUrl.origin;
+}
+
+export async function POST(request: NextRequest) {
+  try {
+    const limited = await rateLimit(request, 'mutate');
+    if (limited) return limited;
+
+    if (!isTrustedSameOriginRequest(request)) {
+      return apiErrors.forbidden('Invalid request origin');
+    }
+
+    const session = await auth();
+    if (!session?.user?.id) {
+      return apiErrors.unauthorized();
+    }
+
+    if (!isStripeConfigured()) {
+      return apiErrors.internalError('Stripe billing is not configured');
+    }
+
+    const billing = await getBillingOverview(session.user.id);
+    if (!billing.subscription.stripeCustomerId) {
+      return apiErrors.badRequest('No Stripe customer exists for this account');
+    }
+
+    const stripe = getStripe();
+    const portalSession = await stripe.billingPortal.sessions.create({
+      customer: billing.subscription.stripeCustomerId,
+      return_url: `${getAppOrigin(request)}/settings`,
+    });
+
+    const response = successResponse({ url: portalSession.url });
+    return withCacheControl(response, 'private, no-store');
+  } catch (error) {
+    console.error('Error creating Stripe portal session:', error);
+    return apiErrors.internalError('Failed to open billing portal');
+  }
+}