Refactor Credit Card schema with spending limits under constraints

Changes

• This update refactors the ApiCard schema to move spending limits into a new constraints property while adjusting the required fields order accordingly.

updated endpoints

• No endpoints were changed.

other changes

• In the ApiCard definition:
  • Added a new constraints property to hold spending limits and other constraints as a nullable object.
  • Removed the standalone spending_limit property.
  • Updated the required fields list to require constraints before currency, and reordered other required fields accordingly.