Allow superadmins to override free device limits and per-device pricing
on a per-organization basis. Overrides cascade through subscription
limits, billing calculations, and user-facing settings display.
- Add custom_free_device_limit and custom_price_per_device to organizations
- Add billing_override_changeset with validation
- Update SubscriptionLimits.effective_device_limit to respect overrides
- Update Billing to use effective free count and price per device
- Add Admin.update_billing_overrides with audit logging
- Add override editing UI to /admin/organizations
- Update org settings page to show effective limits/pricing
Graham McIntire
9aec87636b