Sealed Classes & Status Handling Refactor

### ✨ New Features * **Sealed Classes for Status Handling** * Refactored `GetStatus` to use Dart’s sealed classes for improved type safety and pattern matching * Added **exhaustive pattern matching** with the `match` method * Added **`when` method** for side-effect-based status handling * Added **`mapSuccess`** for transforming success values * Added **`dataOrNull`** and **`errorOrNull`** extensions for safer data access ### 🔧 Improvements * **Type Safety**: Stronger typing across state management APIs * **Documentation**: Comprehensive docs for all public APIs * **Testing**: Extended test coverage for new sealed class implementation * **Performance**: Optimized state updates with efficient equality checks ### ⚠️ Breaking Changes * `GetStatus` is now a **sealed class** with a private constructor * `ErrorStatus` now accepts **only one type parameter** * Custom status implementations must now **extend predefined status classes** * `isCustom` getter only returns `true` for `CustomStatus` instances ### 🛠 Migration Guide #### 1. Pattern Matching Replace `if-else` chains with `match`: ```dart // Before if (status.isLoading) { return LoadingWidget(); } else if (status.isError) { return ErrorWidget(status.errorMessage); } else { return SuccessWidget(status.data); } // After return status.match( loading: () => LoadingWidget(), error: (error) => ErrorWidget(error?.toString() ?? 'Unknown error'), success: (data) => SuccessWidget(data), empty: () => EmptyWidget(), custom: () => CustomWidget(), ); ``` #### 2. Error Status Update usages of `ErrorStatus` with **two type parameters** → now only **one**: ```dart // Before ErrorStatus<MyData, Exception> status; // After ErrorStatus<MyData> status; ``` #### 3. Custom Status Custom implementations should now **extend predefined status classes**. --- ✅ **This PR makes state handling safer, more expressive, and future-proof.**