prepare 2.4.0

[julien-nc]

Changed

• Show image results full width @julien-nc #183
• Use new assistant endpoint to download task output files with mimetype detection, use preview endpoint to display image results @julien-nc #184
• Improve agency action confirmation style+design @julien-nc #194

Fixed

• Update npm pkgs to fix NcSelect with right-to-left languages @janepie #185
• Make assistant modal 'dark' @janepie #180
• Fix choose file button position with RTL languages @julien-nc #186
• Fix UI issues for Context Chat @kyteinsky #190
• Fix(regeneration): store task id in messages so the check endpoint can return a message ID @julien-nc #188