Conversations: Owner message filter in the inbox

Summary: Teams managing both guest experience and owner success in Sparrow need to isolate owner threads from guest threads in the Conversations inbox. Owner communications are assumed not to be ingested or delineated today, so this request covers the full path from ingestion to filtering.

Requested behavior:

1. Ingest owner communications into the Conversations inbox. Audit each supported PMS API for owner-messaging support (what they support and what they do not) and implement ingestion wherever the API allows.

2. Detect and tag owner conversations. Mark owner threads with an owner indicator so they are visually distinguishable from guest threads in the inbox and on the open thread.

3. Filter and route. Add "Owner" as a one-click filter in the left sidebar of the Conversations inbox, in the area where the Urgent label appears today. Expose the owner attribute as a condition in conversation rules and in saved views, so owner messages can be auto-labeled, routed, or escalated to the owner success team.