Import blocks, out-of-service rooms and the waitlist #87

Blocked by: #83

Problem

The nightly import reads only rooms in stock, rooms sold and revenue. It ignores three columns of the Actual & Forecast report that change how a night should be read: group blocks (rooms sold at negotiated prices), rooms out of service, and the waitlist.

Goal

Each night records its blocked rooms, rooms out of service and waitlist, so occupancy uses the rooms that could actually be sold and nights with a waitlist can be spotted.

Scope

• Extend the nightly performance table with blocked rooms, rooms out of service (ROOS) and waitlist count.
• Update the Actual & Forecast parser to read them, plus any other columns confirmed useful in the export review.
• Compute occupancy from sellable rooms (rooms − out of service).
• An Alembic migration that applies and rolls back; existing rows keep working with the new columns empty.

Considerations

• Guestline's Occ% counts out-of-service rooms as unsold, so a fully sold night can show as 99%. Use our own calculation.
• Check that the parser still reads older exports that don't have these columns.

Acceptance criteria

• A sample file loads with blocks, out-of-service rooms and waitlist filled in.
• A fully sold night with rooms out of service shows 100% occupancy.
• The migration upgrades and downgrades cleanly.
• Tests cover the new columns and older files.