Re-designed backend JavaScript and changed handling of data

Fully redesigned the backend JavaScript with the help of Claude Code.
Now it is more next to TYPO3 Core Code.

• [!!!][TASK] replace DataHandler hook by datamap for references
• [!!!][FEATURE] add paste toolbar web component to the page module
• [FEATURE] paste content from other pages also as reference
• [FEATURE] add AJAX route with type and language of a selected content element
• [TASK] execute context menu action with AjaxDataHandler