feat: Add MCP server with 34 tools for AI agent integration

- Add django-mcp-server with 34 tools covering locations, transportations,
  lodging, visits, collections, notes, checklists, templates, and geocoding
- Add API token management endpoint for MCP authentication
- Add MCP token management UI in settings page
- Feature-flagged via mcp_server in INSTALLED_APPS

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: wanoo