Add a setting within the MCP data source config to exclude specific contact fields from MCP requests, rather than only enabling/disabling whole endpoints.

Today the only control is at the command level (e.g. turning off "Get contacts" entirely). But that's all-or-nothing. For HIPAA/PHI reasons I need to expose basic contact data to my AI agent (name, email) while withholding sensitive fields on the same record.

Use case: I run a healthcare company and want Claude connected via MCP for marketing/ops work, but I can't send PHI fields to the AI. Field-level exclusion lets me keep the useful endpoints on while guaranteeing sensitive fields never leave Ortto.

Suggested behavior: a field allowlist/blocklist per MCP data source, applied to all MCP responses.