Cron Activity with wrong expression crashed the Elsa Studio

## Description
I am trying to create a workflow which start with a Cron Job (9pm of every 26th of the month) using Elsa Studio (3.7.0),
When I publish, it crashes with `ApiException: Response status code does not indicate success: 400 (Bad Request).
`
Without Cron activity, the workflow gets published without any issue

## Steps to Reproduce
When click to Publish button after adding the Cron activity (* 21 26 * * ?) Or (* 21 26 * *)

1. **Detailed Steps**:
- Created HttpRequest (GET)
- Tested the request, it works fine
- Add Cron activity before HttpRequest
- Save the workflow
- Publish workflow

2. **Reproduction Rate**:
Every time

3. **Video/Screenshots**:

## Expected Behavior
Publish the workflow and show the success message

## Actual Behavior
Esla Studio crashed with error
`ApiException: Response status code does not indicate success: 400 (Bad Request).`

## Screenshots

## Environment
- **Elsa Package Version**: 3.7
- **Operating System**: Windows 11 (Enterprise).
- **Browser and Version**: Edge Version 149.0.4022.62

## Additional Context
Response from DevTools (Network > Http call response)
`
{
"statusCode": 400,
"message": "One or more errors occurred!",
"errors": {
"generalErrors": [
"Error when parsing cron expression: The given cron expression has an invalid format. Hours: Value must be a number between 0 and 23 (all inclusive)."
]
}
}
`

Start by reproducing the failure in Elsa Studio 3.7.0: add a Cron activity before the HttpRequest and publish using the expressions shown in the issue. Inspect the Publish request in DevTools Network and trace the returned cron-validation error. Done means the workflow publishes successfully, or the invalid expression receives a clear validation message without crashing the Studio.

Written by the indexing model from the issue text.