Support for Booking.com Multi-Inventory Model (Rooms to sell > 1)

Problem: Currently, Hospitable does not support Booking.com listings configured as "multi-inventory" (where the "Rooms to sell" field is greater than 1). This prevents the connection of listings that have multiple identical units.

Current Workaround: The user must create each unit as a separate "Room" (sub-listing) with "Rooms to sell = 1", which is extremely cumbersome to manage for a large number of units (e.g., 24 units).

Impact: Significant time loss during setup and increased complexity in daily property management.

Proposed Solution: Enable native support for Booking.com multi-inventory listings without requiring the creation of individual listings for each unit.

Unlock: Drastic simplification of onboarding and management for hosts with multiple identical units.