Checkout with existing payment method and expanded Snoozing

Added Nice/Elan as a camera system brand option in Site Documentation.

Existing customers can now choose saved payment methods when using Stripe Checkout for subscriptions.

Conversations reply and internal notes inputs are fixed on mobile so you no longer need to scroll horizontally.

Snooze now allows dates beyond one year, and backend validation errors are shown in the UI instead of a generic message.

Recurring on-call escalation notifications now correctly notify the scheduled agent and send Twilio messages or calls; duplicate Slack alerts for the same escalation were reduced.

Stripe Checkout no longer errors in setup mode when creating sessions; saved payment method options are omitted for setup and included for subscription mode.