Update a todo

Updates all fields of an existing todo. This is a full update operation that replaces the entire todo.

Permission Requirements:

• The authenticated user must be an employee or crew member.
• Crew users can only update incomplete todos where they are the assigned user or creator.

Field Restrictions:

• The job field cannot be updated (it can only be set during creation).
• The created_by, company, and audit fields are automatically managed.

Auto-generated Behaviors:

• When a start datetime is provided, an event is created/updated and linked to the todo.
• Tags are automatically deduplicated.