[Calendar MCP] Add support for updating event categories #84
Description
The Calendar MCP currently supports updating most event properties (subject, body, location, time, attendees, importance, sensitivity, recurrence, showAs), but does not expose the categories field on UpdateEvent.
Microsoft Graph API supports updating categories via PATCH /me/events/{id} with a categories array in the body.
Request: Add categories as an optional parameter to the UpdateEvent tool, allowing users to set/update categories on calendar events.
Use case: Bulk-categorizing meetings (e.g., marking all "Focus time" events as "Personal") — currently not possible without direct Graph API access, which is often blocked by org conditional access/token protection policies.