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

backend/internal/handler/client_tenant_access_test.go

@@ -250,7 +250,7 @@ func TestGetConsentRequest_DeniesRestrictedClientWhenProfileResolutionFails(t *t
 			mockKratos := new(MockKratosAdminService)
 			mockKratos.On("GetIdentity", mock.Anything, "user-123").Return(&service.KratosIdentity{
 				ID: "user-123",
-				Traits: map[string]interface{}{
+				Traits: map[string]any{
 					"email":       "user@test.com",
 					"tenant_id":   "tenant-a",
 					"companyCode": "tenant-a",