fix: [KD-17979] replace absoluteFillObject for RN 0.85 WebView overlay

[ethanpschoen]

Description of this change

React Native 0.85 removed StyleSheet.absoluteFillObject. The Ketch WebView overlay container in KetchServiceProvider spread that API for full-screen positioning, so on RN 0.85+ the spread is a no-op and showPreferenceExperience / showConsentExperience can appear not to render. Replaced it with explicit absolute inset styles (position, top, left, right, bottom) and added unit tests that assert the layout and simulate the removed API.

Why is this change being made?

• Chore (non-functional changes)
• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How was this tested? How can the reviewer verify your testing?

• cd package && npm test — 6/6 Jest tests pass, including new styles.test.ts coverage for full-screen container layout and RN 0.85 absoluteFillObject removal simulation.
• iOS example app (run-sample-app.sh ios local on iPhone 17 Pro): Reload → Preferences and Consent — WebView overlay covers the full screen.

Reviewer can repeat with the example app linked to file:../package on this branch.

Related issues

Jira: https://ketch-com.atlassian.net/browse/KD-17979

Checklist

• I have added tests to cover my changes.
• All new and existing tests passed.
• I have evaluated the security impact of this change, and OWASP Secure Coding Practices have been observed.
• I have informed stakeholders of my changes.

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Note

Low Risk
Localized styling change with unit tests; no auth, data, or API behavior changes.

Overview
Fixes full-screen Ketch consent/preference WebView overlays on React Native 0.85+, where StyleSheet.absoluteFillObject was removed so spreading it into KetchServiceProvider container styles no longer applied inset positioning.

The overlay container style now uses explicit position: 'absolute' with top/left/right/bottom: 0 instead of ...StyleSheet.absoluteFillObject. New Jest tests in styles.test.ts lock in the expected layout and document the regression when the old spread is a no-op.

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