feat(delivery): implement white-glove assembly delivery scheduler and quote estimator API

[Babin123456]

Related Issue

Closes #766

Summary

Implements a White-Glove Delivery & Assembly Scheduler Engine for Furnix that handles service level options (Curbside, Room-of-Choice, White-Glove Assembly), appointment time slots, and projected arrival dates.

Changes Made

• Created scripts/white-glove-delivery-scheduler.js with tier configurations and lead time date projections.
• Created scripts/white-glove-delivery-scheduler.test.js with comprehensive unit tests.
• Added POST /api/delivery-quote endpoint to server.js.
• Added delivery card styling rules in style.css.
• Updated docs/CLIENT_API_REFERENCE.md.

Testing

• Executed node scripts/white-glove-delivery-scheduler.test.js (All tests passed).
• Verified transit date projections across weekends.
• Tested API endpoint with various tier and slot combinations.

Impact

Provides luxury fulfillment options and allows customers to schedule tailored assembly services.

Checklist

• Code follows project standards
• Tested locally
• No unrelated changes included
• Responsive design verified
• Accessibility considered

[Babin123456]

@janavipandole Resolved.