perf(dropzone): add virtualization for large DropZone content

[LPIX-11]

Description

This PR adds virtualization support for DropZone content lists to handle scenarios with many heavy components. When rendering 50+ components, especially those with complex nested structures or expensive render cycles, the editor would become sluggish during scrolling and editing. Virtualization ensures only visible components are rendered at any time.

Changes made

• Add @tanstack/react-virtual to virtualize DropZone content exceeding 50 components
• Create VirtualizedContent component to handle windowed rendering

How to test

• Create a DropZone with 100+ (goes as far as 5000) heavy components (e.g., components with nested DropZones, rich text fields, or complex layouts)
• Verify smooth scrolling and responsive editing
• Verify DropZones with <50 components still render normally without virtualization

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Project	Deployment	Review	Updated (UTC)
puck-demo	Ready	Preview, Comment	Jan 21, 2026 8:33am