Add Vacasa to the review source filter

Problem / context

Vacasa reviews now ingest and display in the reviews list, but Vacasa is not available as an option in the review source filter. Users can see the reviews but cannot filter to them. This is an immediate gap for any operator who filters by source to isolate and work a single channel.

Requested capability

Add Vacasa as a selectable option in the review source filter.

Detail / spec

• Vacasa appears alongside the other review sources in the filter.
• Gate behind a feature flag so the option only appears for accounts that could plausibly have Vacasa inventory. It should not appear for accounts with no Vacasa distribution.

Acceptance criteria

• Vacasa appears in the review source filter for eligible accounts.
• Filtering by Vacasa returns Vacasa reviews.
• The option does not appear for accounts without Vacasa inventory.