- Added `submitForApproval` method to `ShiftsRepositoryInterface` and its implementation in `ShiftsRepositoryImpl`.
- Created `SubmitForApprovalUseCase` to handle the submission logic.
- Updated `ShiftsBloc` to handle `SubmitForApprovalEvent` and manage submission state.
- Enhanced `HistoryShiftsTab` and `MyShiftsTab` to support submission actions and display appropriate UI feedback.
- Refactored date utilities for better calendar management and filtering of past shifts.
- Improved UI components for better spacing and alignment.
- Localized success messages for shift submission actions.