Support external submission for embedded CardView

[PrinceD96]

Summary

Allow embedded CardView consumers to hide the native submit button and submit the component from a merchant-owned CTA.

Motivation

CardView currently always renders the native submit button and does not expose an imperative submit API. Checkout screens with a persistent or anchored pay button therefore have to show two submit buttons or maintain a local patch of the SDK.

Proposed solution

• Add card.showSubmitButton?: boolean, defaulting to true, and map it to the iOS and Android Card Component configurations.
• Expose a CardViewHandle ref with submit(): void, matching the imperative submit pattern in Adyen Web.
• Keep the existing callback flow: a successful imperative submission invokes onSubmit with the same data and component proxy as the native button.
• When an embedded submission fails and the merchant calls component.hide(false), stop the native loading state so the same form can be retried; successful completion keeps the existing cleanup behavior.

All existing behavior remains unchanged unless showSubmitButton is explicitly set to false.

Acceptance criteria

• The native Card Component submit button can be hidden on iOS and Android.
• An embedded card can be submitted through a React ref.
• External submission preserves the existing onSubmit callback contract.
• Failed submissions can be retried without remounting the card form.
• Default CardView behavior remains unchanged.
• The public API and configuration docs include the new options.

Alternatives considered

Keeping the native button visible does not work for layouts that already have a primary checkout CTA. Reimplementing card fields outside Components or patching the package locally adds unnecessary integration and maintenance cost.