feat: implement hotel booking mvp

[ideook]

Summary

Implements the hotel booking MVP requested across #1, #2, and #3.

Included:

• PostgreSQL relational schema for users, hotels, room types, rooms, and bookings
• Auth endpoints for register/login/logout with password hashing and session tokens
• Hotel, room type, and room management endpoints for a single hotel admin flow
• Availability endpoint with date overlap checks
• Booking creation endpoint that prevents overbooking by selecting only available rooms
• Node test coverage for auth, availability, booking creation, and room management

Verification

• npm test

Closes #1
Closes #2
Closes #3