Grey out unavailable dates on Multi-Property Search calendar (portfolio union availability)

Problem

On Direct Multi-Property Search (MPS), the date picker leaves all future dates selectable. Guests only learn which properties are available after they pick dates and run a search. Hosts want the calendar to reflect combined portfolio availability up front.

Expected behavior

The MPS calendar should use OR logic across all properties on the site (respecting location filter and guest count):

• If at least one property can host guests on a date, that date stays selectable.
• If no property can host guests on a date, grey out / disable that date.

Example

• Property A available: Sep 1–7, 2026
• Property B available: Sep 1–11, 2026
• Calendar should show Sep 1–11 as selectable; only grey out dates where both properties are unavailable.

Current behavior

MPS only disables past dates and dates beyond the 90-night max. Availability is evaluated after search via GET /bookings/api/properties/search. The single-property Direct booking widget already pre-greys dates via GET /properties/{propertyId}/calendar; MPS was never wired the same way.

Customer context

Reported by Shiny Apple Cabins (shinyapplecabins.com) via support. They want guests to see accurate availability before selecting dates, not only in search results afterward.

Support / Intercom

Intercom conversation 215475494789264

Engineering notes

• No site-level union availability calendar API exists today.
• Union logic must account for min stay, check-in/check-out rules, max guests, pets, and location filters.
• Calendar may need to refresh when guest count or location changes.
• Performance impact for large portfolios (calendar fetch is batched per property).