This PR adds a button to the bottom of the sidebar that opens the
archive view, which at the moment, only shows the same, uncategorized
thread list available in the regular agent panel's history view.

Release Notes:

- N/A

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Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>
Co-authored-by: Bennet Bo Fenner <53836821+bennetbo@users.noreply.github.com>
Co-authored-by: Zed Zippy <234243425+zed-zippy[bot]@users.noreply.github.com>