fix: add resize observer for parent

[htomo1122]

Summary

• Add ResizeObserver to monitor parent element size changes
• Update drag/resize bounds when parent size changes
• Adjust element position and size to stay within parent bounds

Problem

When parent container size changes dynamically, the element's bounds are not updated and can overflow outside the parent.

Solution

• Use ResizeObserver to detect parent size changes
• Recalculate bounds during drag/resize operations
• When parent shrinks: move element to fit, then reduce size if needed (respecting minWidth/minHeight)

Related

Fixes the issue that #429 attempted to address.