Use tabs on the commission page

[rjt-rockx]

As of now, we dump invoices and uploads and other commission data into the side panel, which realistically should rather function as an overview of those sections, given the minimal horizontal screen space we have there. Each section can be moved to its own tab, something like:

• Timeline (the current view)
• Invoice (an up-to-date invoice of the commission so far, with related actions)
• Media (attachments and uploads, sortable and filterable)

[zkat]

This feels like something we should definitely figma first