fix: handle duplicated id error in cron creator

[bcExpt1123]

What this changes

Fixes validation behavior in the cron job dialog:

• Clears existing error messages on input change before re-validating.
• Prevents the Save action from proceeding when validation errors are present.
• Ensures the “ID cannot be empty” error does not persist after fields are corrected.
• Avoids the app crash caused by repeatedly clicking Save while errors exist.

Related Issues

fixes #47

How I tested this

• Reproduced the original issue following the reported steps.
• Verified that:
  • Error messages are cleared when inputs change.
  • Filling all required fields removes the validation error.
  • Clicking Save no longer crashes the app.

Checklist

• I have read CONTRIBUTING.md and this PR follows the guidelines
• A human has reviewed the entire diff of this PR, every line of code
• A human understands the changes and can explain why this approach is correct
• This PR doesn't have AI-generated boilerplate or co-author lines
• This PR was authored and submitted by an AI agent without human review

[antoniorodr]

Hello @bcExpt1123!

Thank you so much for this. It looks good to me, so I will merge it locally to a new branch. I do not want to release a new version just yet, but I will make sure to include this in the next release.