Select existing users in the Manage Collaborators dialog

Describe the feature you'd like

Allow list owners to select an existing user from the Manage Collaborators dialog instead of requiring their email address to be entered manually.

The dialog could show or search users who already have accounts on the same Karakeep instance. Entering an email address could remain available when the required user is not listed.

My instance has only two users, but I still need to enter the other user's email each time I share a list.

Describe the benefits this would bring to existing Karakeep users

This would make sharing lists faster and reduce mistakes caused by manually entering email addresses.

It would particularly help families, households, and small self-hosted instances where the same people collaborate on several lists. These users already have accounts, so selecting them directly is more natural than repeatedly treating them as new email invitees.

Can the goal of this request already be achieved via other means?

Partially.

A list owner can invite an existing user by entering the email address associated with their account. This works, but the owner must already know and repeatedly enter the correct address.

There does not appear to be a way to browse or search existing users from the Manage Collaborators dialog.

Have you searched for an existing open/closed issue?

• I have searched for existing issues and none cover my fundamental request

Additional context

Related issue: https://github.com/karakeep-app/karakeep/issues/37

That issue introduced collaborative lists through PR #2146. This request is a smaller improvement to the existing Manage Collaborators workflow.