docs: add detailed explanation about paginate() and beforeFind model event

[michalsn]

Description
This PR adds a note explaining the potential inconsistency when using the Model::paginate() method in combination with the beforeFind event. It aims to help prevent confusion when paginate() is used alongside query-modifying events.

Resolving this issue is non-trivial, as it would require a careful redesign of the pagination logic or parts of the model to ensure consistent behavior across both data retrieval and counting queries.

Due to this complexity, we are not applying a framework-level fix at this time. Instead, this note provides clear guidance so that developers are aware of the behavior and can plan accordingly.

This note will remain in place to support users until a long-term solution is identified and adopted.

Closes #9617

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[neznaika0]

Nice.