Add Person and Status field types

## Goal

Two field types Cortext doesn't have today. Person stores one or more WP user references per row (Assignee, Reviewer, Reporter, and so on). Status is a select-with-workflow-groups, which is what board grouping actually wants.

## Scope

* Person field type:
* Stores one or more WP user IDs in row meta.
* A picker UI that searches WP users by display name.
* Single or multi configurable per field.
* Renders as user chips with avatar.
* Status field type:
* Select-style options grouped into workflow buckets ("To-do", "In progress", "Done"), configurable per field.
* Default groups so new fields ship with sensible workflows.
* The board layout groups by Status's workflow buckets when Status is the chosen group-by field.
* Filter and sort on Person (by user) and Status (by group, by option).
* Status workflow groups and Person's single/multi setting are managed from the per-field config panel.

## Out of scope

* Notification on assignment.
* Permissions tied to Person fields.
* Workspace user directory beyond WP users.

## Acceptance criteria

* You can add a Person field, configure single or multi, and assign WP users to rows.
* You can add a Status field with custom groups; rows pick a status from any group.
* The board layout grouped by Status uses the workflow buckets.
* Filter and sort work on both types.