Add Stripe payment integration and update configuration

- Added Stripe environment variables to docker-compose.yml for secret key, webhook secret, and base URL.
- Created PAYMENTS.md to document the setup and usage of the Stripe payment system.
- Updated webhook signature handling in stripe.js to use a new secret key.

Signed-off-by: Omar Sánchez Pizarro <omar.sanchez@pistacero.net>

docker-compose.yml

@@ -37,6 +37,9 @@ services:
       - MONGODB_DATABASE=wallabicher
       - MONGODB_USERNAME=admin
       - MONGODB_PASSWORD=adminpassword
+      - STRIPE_SECRET_KEY=sk_test_51SrpOfH73CrYqhOp2NfijzzU07ADADmwigscMVdLGzKu9zA83dsrODhfsaY1X4EFTSihhIB0lVtDQ2HpeOfMWTur00YLuuktSL
+      - STRIPE_WEBHOOK_SECRET=whsec_8ebec8c2aa82a791aa9f2cd68211e297a5d172aea62ebd7b771d230e3a597aa8
+      - BASE_URL=https://wb.pribyte.cloud/api
     volumes:
       # Montar archivos de configuración y datos en ubicación predecible
       - ./config.yaml:/data/config.yaml:ro