Add ensemble.storage.clear() method

[sharjeelyunus]

Description

Adds a clear() method to ensemble.storage that removes all normal storage values at once, enabling developers to reset persisted local storage data when needed.

Related Issue

Fixes #2187

Type of Change

• 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 change)
• Documentation update
• Refactoring (no functional changes)

What Has Changed

• storage_manager.dart (PublicStorage mixin): Added getKeys() to retrieve all public storage keys, and clearPublicStorage() to remove all non-encrypted entries from the public GetStorage container.
• data_context.dart (EnsembleStorage): Added clear() method that clears all normal storage keys and dispatches StorageBindingSource change events for each removed key so UI bindings refresh. Registered 'clear' in the methods() map.
• test/storage_manager_test.dart: Added 5 unit tests covering the clear logic — filtering, empty storage, mixed keys, encrypted key preservation, and post-clear usability.

API

ensemble.storage.clear();

Behavior

• Removes all values stored through ensemble.storage
• Preserves encrypted storage (enc_ prefixed keys in the same GetStorage box)
• Does not touch secure storage (FlutterSecureStorage), system storage (GetStorage('system')), keychain values, secrets, or environment variables
• Dispatches StorageBindingSource change events for each cleared key so UI expressions/bindings update correctly
• Works consistently across web, iOS, and Android (uses GetStorage which is cross-platform)
• Existing get, set, delete methods continue to work after clearing

How to Test

1. Run melos bootstrap from the repo root
2. Run flutter test test/storage_manager_test.dart in modules/ensemble/ — 5 tests should pass
3. Run flutter test in modules/ensemble/ — all 88 tests should pass
4. In a running app, call ensemble.storage.clear() after setting some values — all values should be removed and any UI bindings should update

Checklist

• I have run flutter analyze and addressed any new warnings
• I have run flutter test and all tests pass
• I have tested my changes on the relevant platform(s)
• I have updated documentation if needed
• My changes do not introduce new warnings or errors