This update modernizes contract onboarding by shifting the experience and terminology from contracts to subscriptions across sales, website, and dashboard areas. It makes subscription setup more product-driven, improves sales order handling, and simplifies the customer portal by removing plan-change flows that are no longer needed.

Description of the issue/feature this PR addresses:

Task: https://www.odoo.com/web?#id=29701&view_type=form&model=project.task&action=333&active_id=131&menu_id=4720
Pad: https://pad.odoo.com/p/r.57a8de8fbdfa47be6c6e31d65412d759