Feature: #107240 - Add warning when pasting password with whitespace

Description

A new warning mechanism has been introduced in the backend login form to help users avoid authentication issues when pasting passwords that contain leading or trailing whitespace.

When a password is pasted into the backend login form, the system now detects if the pasted text contains leading or trailing whitespace characters (spaces, tabs, newlines, etc.) and displays a warning message to the user.

The warning includes an action button that allows users to automatically remove the surrounding whitespace from the pasted password, ensuring successful login attempts.

This feature helps prevent common login failures caused by accidentally copying whitespace along with passwords from password managers, text editors, or other sources.

The implementation includes:

• Detection of leading and trailing whitespace in pasted passwords
• Visual warning message displayed to the user
• One-click action to remove the surrounding whitespace

Example

The whitespace detection covers various whitespace characters including:

• Regular spaces (U+0020)
• Tabs (U+0009)
• Line breaks (U+000A, U+000D)
• Other Unicode whitespace characters

Impact

Users will now receive immediate feedback when pasting passwords with surrounding whitespace, reducing login failures and improving the overall user experience when authenticating to the TYPO3 backend.