Implement Auto-save in Environment Editor

[soovittt]

Description

No auto-save functionality. Users can lose work if browser crashes or tab is closed.

Current State

• No auto-save
• Manual save only
• Risk of data loss

Files Affected

• app/components/EnvironmentEditor.tsx - Editor component
• app/lib/sceneClient.ts - Save functionality

Expected Behavior

• Auto-save changes periodically (e.g., every 30 seconds)
• Auto-save on significant changes
• Visual indicator of save status
• Recovery of unsaved changes on page reload
• Configurable auto-save interval

Acceptance Criteria

• Implement auto-save mechanism
• Add periodic auto-save
• Add auto-save on changes
• Add save status indicator
• Add unsaved changes recovery
• Add configurable interval
• Add tests