Pull Request for Issue #46655 .

Description

This PR adds support for an exclude attribute to the category form field type, allowing developers to exclude specific category IDs from the dropdown list.

Problem Statement

Developers often need to exclude certain categories (like "Uncategorized") from category selection lists in forms. Previously, there was no built-in way to do this with the standard category field type.

Solution

Added an exclude attribute that accepts a comma-separated list of category IDs to exclude from the options.

Usage Example

<field 
    name="category" 
    type="category" 
    extension="com_content" 
    exclude="1,5,10" 
    label="Select Category" 
/>

Implementation Details

• Added filtering logic in the getOptions() method of CategoryField class
• The exclude attribute accepts comma-separated category IDs
• Category IDs are properly sanitized using intval()
• Filtering is only applied when the exclude attribute is set and contains valid IDs

Testing

The implementation follows the same pattern as the custom field provided in issue #46655 and has been tested to ensure:

• Categories specified in the exclude attribute are properly filtered out
• Empty or invalid exclude values are handled gracefully
• The field continues to work normally when no exclude attribute is present

Closes #46655