feat: add ShiftAssignmentCard widget and StaffShifts module

- Implemented ShiftAssignmentCard widget for displaying shift assignments with client details, pay calculation, and confirmation actions.
- Created StaffShiftsModule to manage dependencies, routes, and use cases related to staff shifts.
- Added necessary dependencies in pubspec.yaml and generated pubspec.lock.

apps/mobile/packages/features/staff/staff_main/lib/src/staff_main_module.dart

@@ -10,6 +10,7 @@ import 'package:staff_tax_forms/staff_tax_forms.dart';
 import 'package:staff_documents/staff_documents.dart';
 import 'package:staff_certificates/staff_certificates.dart';
 import 'package:staff_attire/staff_attire.dart';
+import 'package:staff_shifts/staff_shifts.dart';
 
 import 'package:staff_main/src/presentation/blocs/staff_main_cubit.dart';
 import 'package:staff_main/src/presentation/constants/staff_main_routes.dart';
@@ -28,10 +29,9 @@ class StaffMainModule extends Module {
       '/',
       child: (BuildContext context) => const StaffMainPage(),
       children: <ParallelRoute<dynamic>>[
-        ChildRoute<dynamic>(
+        ModuleRoute<dynamic>(
           StaffMainRoutes.shifts,
-          child: (BuildContext context) =>
-              const PlaceholderPage(title: 'Shifts'),
+          module: StaffShiftsModule(),
         ),
         ChildRoute<dynamic>(
           StaffMainRoutes.payments,