Autocalls AI + Mattermost Integration

Keep Autocalls AI and Mattermost aligned: when communication events happen in one, update the other automatically.

Example: when Autocalls AI's "Watch Calls" fires, WEXTL can "Acknowledge Post" in Mattermost. Autocalls AI has 3 triggers (including Watch Calls, Watch Inbound Events, and Watch Leads); Mattermost has 146 actions (including Acknowledge Post, Add User to Channel, and Add User to Team).