docs: Add CHANGELOG.md files to all federated plugin packages

- Add CHANGELOG.md to workmanager_platform_interface
- Add CHANGELOG.md to workmanager_android
- Add CHANGELOG.md to workmanager_ios

Each package now has its own changelog documenting the initial 0.8.0
release with federated plugin architecture migration.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ened

workmanager_android/CHANGELOG.md

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+## 0.8.0
+
+* **BREAKING**: Migrate to federated plugin architecture
+* Initial release of the Android implementation
+* Implement all `WorkmanagerPlatform` methods for Android
+* Support for one-off and periodic tasks using WorkManager API
+* Support for constraints: network type, battery not low, charging, device idle, storage not low
+* Support for backoff policies: linear and exponential
+* Add `isScheduled` method to check if a periodic task is scheduled (Android only)
+* Migrate from `be.tramckrijte` to `dev.fluttercommunity` namespace

workmanager_ios/CHANGELOG.md

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+## 0.8.0
+
+* **BREAKING**: Migrate to federated plugin architecture
+* Initial release of the iOS implementation
+* Implement all `WorkmanagerPlatform` methods for iOS
+* Support for one-off tasks using BGTaskScheduler API
+* Support for processing and refresh tasks
+* Fix optional `initialDelaySeconds` parameter handling
+* Add debug notification helper for testing
+* Add thumbnail generator for background tasks
+* Migrate from `be.tramckrijte` to `dev.fluttercommunity` namespace

workmanager_platform_interface/CHANGELOG.md

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+## 0.8.0
+
+* **BREAKING**: Migrate to federated plugin architecture
+* Initial release of the platform interface package
+* Define `WorkmanagerPlatform` abstract class with all method signatures
+* Define data classes: `WorkmanagerConfig`, `Constraints`, `BackoffPolicy`
+* Add comprehensive documentation for all public APIs