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/repository/client_consent_repository.go

@@ -44,7 +44,7 @@ func (r *clientConsentRepo) Find(ctx context.Context, clientID, subject string)
 func (r *clientConsentRepo) Upsert(ctx context.Context, consent *domain.ClientConsent) error {
 	return r.db.WithContext(ctx).Unscoped().
 		Where("client_id = ? AND subject = ?", consent.ClientID, consent.Subject).
-		Assign(map[string]interface{}{
+		Assign(map[string]any{
 			"granted_scopes": consent.GrantedScopes,
 			"updated_at":     gorm.Expr("NOW()"),
 			"deleted_at":     nil,