Import/Export surveys via JSON

This feature adds JSON-based import and export capabilities to the poll plugin, enabling editors to efficiently create, transfer, and maintain polls outside the CMS. Polls, including their structure, questions and metadata, can be exported as JSON files and re-imported at any time. This allows for bulk editing, version control, reuse across environments, and easier collaboration between teams. The JSON format ensures a standardized, machine-readable representation of poll content while preserving compatibility with existing poll functionality.