Add button in table should trigger validation

[Aidajafarbigloo]

Currently, clicking the Add button in the table does not trigger any validation or error message when all fields are empty.

Expected Behavior:

• An error message should be triggered (e.g., via toast notification).
• The Add button should only be enabled or functional when at least one of the following field combinations is filled:
  • Identifier + Given Name + Family Name
  • Given Name + Family Name + Email
    (Note: Affiliation is optional in both cases.)

Suggested Fix:

• Add form validation to ensure one of the required combinations is provided.
• Display validation feedback, preferably as toast notifications.
• Disable the Add button (or show validation errors) until the criteria are met.

[Aidajafarbigloo]

It should also solve #183