refactor: Migrate MPRoktEvent

[BrandonStalnaker]

Background

• Part of the ongoing effort to migrate the SDK to source-based distribution instead of shipping as binaries
• Swift files in the main SDK target create complications for SPM source distribution due to mixed-language framework limitations
• Converting public Swift classes to Objective-C enables cleaner source-based integration for customers

What Has Changed

• Converted MPRoktEvent.swift to Objective-C (MPRoktEvent.h and MPRoktEvent.m)
• All 14 event classes (MPRoktEvent, MPRoktInitComplete, MPRoktShowLoadingIndicator, MPRoktHideLoadingIndicator, MPRoktPlacementInteractive, MPRoktPlacementReady, MPRoktOfferEngagement, MPRoktOpenUrl, MPRoktPositiveEngagement, MPRoktPlacementClosed, MPRoktPlacementCompleted, MPRoktPlacementFailure, MPRoktFirstPositiveEngagement, MPRoktCartItemInstantPurchase) are now implemented in Objective-C
• Added comprehensive unit tests for all event types in MPRoktEventTests.m
• Updated existing test file imports to reference the new header

Checklist

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

Reference Issue (For employees only. Ignore if you are an outside contributor)

• Closes https://rokt.atlassian.net/browse/SDKE-868

[github-actions]

📦 SDK Size Impact Report

Measures how much the SDK adds to an app's size (with-SDK minus without-SDK).

Metric	Target Branch	This PR	Change
App Bundle Impact	1.63 MB	1.61 MB	-20 KB
Executable Impact	896 bytes	896 bytes	+N/A
XCFramework Size	6.65 MB	6.41 MB	-240 KB

➡️ SDK size impact change is minimal.

Raw measurements

Target branch (workstation/9.0-Release):

{"baseline_app_size_kb":84,"baseline_executable_size_bytes":75464,"with_sdk_app_size_kb":1752,"with_sdk_executable_size_bytes":76360,"sdk_impact_kb":1668,"sdk_executable_impact_bytes":896,"xcframework_size_kb":6808}

This PR:

{"baseline_app_size_kb":84,"baseline_executable_size_bytes":75464,"with_sdk_app_size_kb":1732,"with_sdk_executable_size_bytes":76360,"sdk_impact_kb":1648,"sdk_executable_impact_bytes":896,"xcframework_size_kb":6568}

[jamesnrokt]

Looks good. One question on the migration docs

[nickolas-dimitrakas]

LGTM