Update helium-swift SDK to 4.5.1

[github-actions]

Automated update of helium-swift SDK dependency to version 4.5.1.

Changes:

• Updated Package.swift dependency version
• Updated podspec dependency version
• Bumped helium_flutter pubspec.yaml version (patch increment)
• Bumped helium_revenuecat pubspec.yaml version (patch increment)
• Updated heliumFlutterSdkVersion constant
• Added changelog entries to both packages

This PR was automatically created by the iOS SDK release workflow.

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Note

Low Risk
Dependency and version-metadata changes only; no application logic or public API changes in the diff.

Overview
Automated iOS native SDK bump from helium-swift 4.4.8 → 4.5.1, with matching 3.3.5 patch releases for helium_flutter and helium_revenuecat.

iOS integration pins are updated in Package.swift and helium_flutter.podspec. Dart-side heliumFlutterSdkVersion and both packages’ pubspec.yaml versions are aligned, with changelog entries noting the dependency update. No Flutter/Dart API or plugin logic changes appear in this diff.

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