add bulk users

internal/contract/user_contract.go

@@ -174,3 +174,10 @@ type BulkCreationSummary struct {
 	Succeeded int `json:"succeeded"`
 	Failed    int `json:"failed"`
 }
+
+// BulkCreateAsyncResponse represents the immediate response for async bulk creation
+type BulkCreateAsyncResponse struct {
+	JobID   uuid.UUID `json:"job_id"`
+	Message string    `json:"message"`
+	Status  string    `json:"status"`
+}