Add Luxora hotel showcase demo

[faruqso]

Summary

• Demo id / title: luxora-hotel / Luxora Low-Poly Hotel
• One-line summary: A code-only low-poly hotel diorama reconstructed as a procedural Three.js object.
• Author (display name) / author URL: Faruq So / https://github.com/faruqso

Contributor checklist

• Reference image rights: contributor-provided reference image, submitted with permission for this showcase PR
• Generated via the img2threejs skill (version: 1.5.0)
• npm run build passes locally
• Screenshot of the rendered demo attached below (preview verified locally)
• Only touched src/demos/luxora-hotel/, public/references/luxora-hotel.jpg, and appended to src/demos/registry.ts (plus the shared hidden-control CSS fix)
• New registry entry has every DemoEntry field filled and status: 'final'

Screenshot

The rendered local preview was verified with:

• 14 selectable hotel parts
• Part detail selection and clear selection
• Explode parts → Assemble reset
• No weapon-specific scope, fire, or bipod controls

Maintainer review

• Visual fidelity acceptable against the reference image
• License/rights statement plausible; no PII or trademark-as-primary-subject issue
• status: 'final' (not left as 'placeholder')
• Bundle size delta looks sane
• pr-safety-check is green

[hoainho]

Hi @faruqso please help to resolve the conflict