Add CRM Manager and round-robin lead-skip via CRM contact ownership

Add CRM Manager and round-robin lead-skip via CRM contact ownership: a task in bird-critic-1.5-full-300 (Harbor dataset). Cal.com has several CRM integrations (Salesforce, HubSpot, Close.com, Pipedrive, Zoho). Today each CRM app handles contact lookups and event creation inside its own service…

The task

Cal.com has several CRM integrations (Salesforce, HubSpot, Close.com, Pipedrive, Zoho). Today each CRM app handles contact lookups and event creation inside its own service class with no shared abstraction. This PR introduces a `CrmManager` wrapper that centralises CRM operations and wires them into availability slot…

Part of kochsnow/bird-critic-1.5-full-300.