List view, sorting by modified date, and filter menu fixes

This release adds a list view for browsing assets, folders, and collections, adds sorting by modified date, and fixes issues with filter menus, signing key errors, and aspect previews.

You can now switch between the existing grid and a compact list view when browsing the Media Library. The list shows folders, collections, and assets together in one keyboard-navigable list. Folders expand inline to reveal their subfolders, collections, and assets. Your choice of view is remembered between sessions, and grid remains the default.

The sort menu now includes Recently modified and Least recently modified. Both work in grid and list view.

• Nested filter menus are now sized against the viewport. Previously, an aspect's submenu was limited to the height of the menu that opened it, and sometimes showed a single scrollable row.
• When creating a signing key fails, you now see the actual reason, including a permissions message if your role can't manage signing keys. Previously, every failure said the key name was invalid.
• Aspects with an array of global document references now show each referenced document's title and subtitle, instead of "undefined".
• When you edit a nested object aspect, the first breadcrumb now shows the asset title instead of "Untitled", and updates when the title changes.
• Filters that hide every collection now show the "no results" state instead of an empty grid.Fixed nested filter menus being squeezed to the height of the menu that opened them. An aspect's submenu could show a single scrollable row; submenus are now sized against the viewport.