fix: resolution of THREE.Clock deprecation, object URL leaks & deferred module initialisation

[Ming2k8-Coder]

Description

This PR resolves several key bugs and performance/memory issues in the core viewer:

• Performance & Deprecations: Replaces deprecated THREE.Clock with high-precision performance.now() delta tracking to eliminate Three.js runtime deprecation warnings.
• Initialization Fix: Removes redundant DOMContentLoaded listener inside deferred ES module scripts to ensure reliable execution across all browsers.
• Memory Leak Fix: Implements an Object URL registry that tracks and revokes Blob URLs upon loading new VRM models.
• Accessibility & UX: Adds aria-expanded attribute synchronization to the panel collapse button.
• Metadata: Adds Open Graph tags, meta description, and an inline SVG favicon to prevent 404 console errors.

Diff Size

~51 lines changed in index.html.