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/service/headless_jwks_cache.go

@@ -309,7 +309,7 @@ func (s *HeadlessJWKSCacheService) refreshClient(ctx context.Context, client dom
 		updated := *previous
 		updated.JWKSURI = jwksURI
 		updated.LastCheckedAt = &now
-		updated.ExpiresAt = ptrTime(now.Add(s.TTL))
+		updated.ExpiresAt = new(now.Add(s.TTL))
 		updated.NextRetryAt = nil
 		updated.LastRefreshStatus = "success"
 		updated.LastError = ""
@@ -339,7 +339,7 @@ func (s *HeadlessJWKSCacheService) refreshClient(ctx context.Context, client dom
 		ClientID:                     client.ClientID,
 		JWKSURI:                      jwksURI,
 		CachedAt:                     &now,
-		ExpiresAt:                    ptrTime(now.Add(s.TTL)),
+		ExpiresAt:                    new(now.Add(s.TTL)),
 		LastCheckedAt:                &now,
 		NextRetryAt:                  nil,
 		LastSuccessfulVerificationAt: previousLastVerification(previous),
@@ -379,7 +379,7 @@ func (s *HeadlessJWKSCacheService) persistRefreshFailure(client domain.HydraClie
 		state.ConsecutiveFailures = previous.ConsecutiveFailures + 1
 	}
 	if s.shouldBackoff(state.ConsecutiveFailures) {
-		state.NextRetryAt = ptrTime(now.Add(s.failureBackoffDuration()))
+		state.NextRetryAt = new(now.Add(s.failureBackoffDuration()))
 	}
 	_ = s.SaveState(client.ClientID, state)
 	return &state
@@ -480,8 +480,9 @@ func previousLastVerification(previous *domain.HeadlessJWKSCacheState) *time.Tim
 	return previous.LastSuccessfulVerificationAt
 }
 
+//go:fix inline
 func ptrTime(value time.Time) *time.Time {
-	return &value
+	return new(value)
 }
 
 func (w *HeadlessJWKSCacheWorker) Start(ctx context.Context) {