Fix: Forward StoreTransaction in RevenueCatUI paywall completion callbacks

[ammadakhtar]

Checklist

• If applicable, unit tests
• If applicable, create follow-up issues for purchases-android and hybrids

Motivation

Resolves #4007

Fix: RevenueCatUI presenter/footer purchase completion callbacks dropping the StoreKit transaction.
PaywallView already supports a transaction-aware purchase completion, but the presenter/footer APIs only forwarded CustomerInfo, preventing apps from accessing transaction metadata.

Description

• Added backward-compatible, additive APIs to expose a transaction-aware purchase completion closure: (StoreTransaction?, CustomerInfo) -> Void.
• Updated presenter + footer wiring to use the 2-arg .onPurchaseCompleted { transaction, customerInfo in ... } so transactions are forwarded when available.
• Fallback to legacy purchaseCompleted still intact.

[ammadakhtar]

Hi @rickvdl
QQ: does the CI checks run after review? And do we have to request reviews or its auto assigned via codeowners or something like that?

First time pushing a PR for RC so new to the flow here :)

[ajpallares]

Hi @ammadakhtar. Thank you so much for your contribution! Very needed indeed, so we'll be taking a look at this as soon as possible!

does the CI checks run after review?

For security reasons, only PRs created by RevenueCat members can trigger the CI runs. But don't worry about that, we'll make sure all CI checks pass before merging into main.

do we have to request reviews or its auto assigned via codeowners or something like that?

Exactly, you don't need to request the review as it is auto-assigned via codeowners.