:sparkles: Add typeahead search in cmd palette

[foysalit]

Backend PR needs to be merged first https://github.com/bluesky-social/atproto/pull/2612

This PR triggers a user typeahead search from command palette when the search query starts with @ allowing moderators to look at a list of users and pick one to action on.

https://github.com/bluesky-social/ozone/assets/1919066/704e5c7b-6bda-4346-9900-39a34b32fd79

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