feat(user): support fixed UUID registration and enhance bulk import results

- Added support for fixed UUIDs during bulk registration (Search-first + ExternalID mapping)
- Implemented idempotency and visibility restoration for soft-deleted users
- Enhanced bulk upload UI to show 'New/Updated/Unchanged' status and modified fields
- Added logic to reclaim identifiers (login_id) from colliding records
- Added frontend E2E and backend unit tests for UUID integrity and conflict handling
- Fixed i18n, formatting, and mock tests to satisfy code-check
- Applied 'go fix' for 'omitzero' tags and general Go standards

locales/en.toml

@@ -1739,6 +1739,17 @@ additional = "Additional Affiliated/Manageable Tenants"
 primary = "Representative Affiliated Tenant"
 title = "Affiliation & Organization Info"
 
+[ui.admin.users.field]
+department = "Department"
+grade = "Grade"
+jobtitle = "Job Title"
+name = "Name"
+phone = "Phone"
+position = "Position"
+role = "Role"
+status = "Status"
+tenant = "Tenant"
+
 [ui.admin.users.list]
 add = "User Add"
 bulk_import = "Bulk Import"
@@ -2878,6 +2889,8 @@ title = "Login request status by company and app"
 export = "Export"
 
 [ui.admin.users.bulk]
+modified_fields = "Modified Fields:"
+no_changes = "No changes"
 permission_placeholder = "Select permission"
 status_placeholder = "Select status"