Add customFields support for contact create/update tools

[marcel10100]

Feature Request

Problem

The create_contact, update_contact, and upsert_contact MCP tools do not support setting custom field values on contacts. The GHL API supports this, but the MCP tool schemas don't expose the customFields parameter.

Current Behavior

• Custom fields cannot be set when creating or updating contacts via MCP
• The upsert_contact implementation passes customFields internally but doesn't expose it in the tool schema

Proposed Solution

Add customFields parameter to the following tools:

• create_contact
• update_contact
• upsert_contact

Format

{
  "customFields": [
    {"id": "field_id", "value": "field value"},
    {"key": "contact.field_key", "value": "field value"}
  ]
}

Note: The GHL API expects value not field_value in the customFields array.

Files to modify

• src/types/ghl-types.ts - Add customFields to MCPCreateContactParams and MCPUpdateContactParams
• src/tools/contact-tools.ts - Add customFields to tool schemas and implementations

Additional context

This would enable setting form field data (Year/Make/Model, Title/Certificate of Origin, Financing, etc.) on contacts via the API.