feat: add staff tax forms module with I-9 and W-4 forms

- Created staff_tax_forms_module.dart to manage tax forms feature.
- Implemented routes for TaxFormsPage, FormI9Page, and FormW4Page.
- Added mock repository for tax forms.
- Established necessary dependencies in pubspec.yaml.
- Exported module in staff_tax_forms.dart.

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

@@ -6,6 +6,7 @@ import 'package:staff_profile_info/staff_profile_info.dart';
 import 'package:staff_emergency_contact/staff_emergency_contact.dart';
 import 'package:staff_profile_experience/staff_profile_experience.dart';
 import 'package:staff_bank_account/staff_bank_account.dart';
+import 'package:staff_tax_forms/staff_tax_forms.dart';
 
 import 'package:staff_main/src/presentation/blocs/staff_main_cubit.dart';
 import 'package:staff_main/src/presentation/constants/staff_main_routes.dart';
@@ -53,5 +54,6 @@ class StaffMainModule extends Module {
     r.module('/emergency-contact', module: StaffEmergencyContactModule());
     r.module('/experience', module: StaffProfileExperienceModule());
     r.module('/bank-account', module: StaffBankAccountModule());
+    r.module('/tax-forms', module: StaffTaxFormsModule());
   }
 }