Add platform-level user management via MCP (list_app_users, update_app_user)

My Iris sub-agent handles tier-one customer support across all 135 apps. Today it queries UserProfile entities, but those are app-defined shapes — not the Base44 auth layer itself. Support operations like tier changes, access revocation, or email corrections require platform-level user primitives.

Requested primitives:

• list_app_users({ appId, filter }) — enumerate users for a given app

• update_app_user({ appId, userId, fields }) — safely update user state

These give support agents a clean, auditable surface to act on without going through app-specific entity gymnastics.

Thank you.