feat: update rokt example validation flow

[denischilik]

Background

This branch updates the Flutter SDK example flow used to validate Rokt placement rendering and event delivery across iOS and Android. It also aligns iOS native dependencies with the current Rokt payment extension path needed for shoppable ads testing.

What Has Changed

• Added explicit Flutter-to-native Rokt event subscription bridging so apps can subscribe by placement identifier.
• Removed implicit native event subscriptions from placement selection calls to avoid duplicate event delivery.
• Updated the example app to exercise shoppable ads using the current iOS test identifier and event listener wiring.
• Added iOS RoktPaymentExtension pod in the example app to support shoppable ads payment-extension setup.
• Refreshed lockfiles and example runtime config generated by local Flutter validation runs.

Screenshots/Video

N/A

Checklist

• I have performed a self-review of my own code.
• I have made corresponding changes to the documentation.
• I have added tests that prove my fix is effective or that my feature works.
• I have tested this locally.

Additional Notes

Validated with local iOS and Android flutter run sessions, including successful selectPlacements flow and Rokt event logs.

[cursor]

PR Summary

Medium Risk
Changes Rokt event delivery semantics from implicit subscription to explicit events(identifier, ...) registration, which can affect integrations if not updated. Also bumps iOS dependency requirements and example iOS pods for shoppable ads payment flows.

Overview
Rokt event delivery now requires explicit subscription by identifier. Adds a new Dart API Rokt.events(identifier, onEvent) that bridges to a new roktSubscribeToEvents native method on iOS/Android, and removes the previous implicit event subscription that happened during selectPlacements/selectShoppableAds.

Updates docs and the example app to wire event listeners before selecting placements/shoppable ads, adds an iOS shoppable-ads validation flow (including sample attributes), and aligns iOS setup by requiring mParticle-Apple-SDK ~> 9.1 plus adding the RoktPaymentExtension pod for payment-extension testing. Lockfiles and Xcode scheme settings are refreshed accordingly.

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