Top up tokens

Purchase additional tokens when the org balance is low.

Subscriptions include a recurring token allowance. Organizations can buy one-time token top-ups via Stripe Checkout when usage exceeds the included balance.

POST /api/organizations/{organizationId}/agents/{agentId}/token-topup/checkout
Cookie: session=...

Response: { "url": "https://checkout.stripe.com/..." }

After payment, the webhook credits the organization token balance for that agent. Token consumption during chat is enforced against this balance.