Add a dispose() method to properly release resources and clean up when a BpmnVisualization instance is no longer needed.

Key changes:
- Add Disposable interface for objects that can free resources
- Implement dispose() in BpmnVisualization to clean up graph and navigation resources
- Add dispose() to NavigationImpl and ZoomSupport to properly remove event listeners
- Prevent loading after disposal with clear error message
- Add integration tests to verify dispose functionality

This is particularly useful for:
- Removing BPMN diagrams from the page and freeing memory
- Cleaning up or unmounting components that use BpmnVisualization
- Preventing memory leaks from event listeners in long-running applications