Add PaywallListener convenience prop to PaywallView components

[rickvdl]

Summary

• Adds PaywallListener and PurchaseResumable interfaces matching the Capacitor SDK definitions
• Adds listener prop to PaywallView and PaywallFooterContainerView as a convenience alternative to passing individual callback props
• Individual callback props take precedence over listener callbacks when both are provided
• No native changes required — purely TypeScript-level convenience

Related PRs

• Based on: Add custom PurchaseLogic support to PaywallView component #1607 (PurchaseLogic support for PaywallView)
• Capacitor equivalent: [SDK-4264] Add PaywallListener and PurchaseLogic to purchases-capacitor-ui purchases-capacitor#688

Test plan

• Verify TypeScript compiles without errors
• Verify API testers pass type-checking
• Test listener prop on PaywallView — purchase/restore callbacks fire
• Test that individual callback props override listener callbacks
• Test that omitting listener doesn't regress existing behavior (existing "Go to Paywall Screen" works as before)

[tonidero]

I think this makes sense! It should make adding more callbacks much nicer as well in the future. Just a comment about deprecating the older APIs.

[tonidero]

Should we deprecate these other methods in favor of using the listener? I think keeping both can be very confusing, that way we can move people to use our preferred approach (which I think should be the listener).

[tonidero]

Hmm I do wonder whether we should add it to the footer... But I think it's ok to keep it. Same comment about deprecating older callbacks in favor of the listener though.