Add sidebar settings view mode

[priethor]

What

Adds a new Settings view mode and moves Import and Published to its sidebar, which can be opened with a cog icon.

Old links keep working: ?p=/import, ?p=/published, and ?p=/settings now land on the new settings routes.

Why

This opens the door to add more settings. Import and Published were too permanent in the quick actions, and they now have a proper place to be.

Testing Instructions

1. Open Cortext and check that the sidebar quick actions show only Search and Home.
2. Click the Settings gear in the sidebar footer.
3. Confirm the settings nav slides in and shows Back plus Import.
4. Open Import and Published, when available, and confirm the canvas changes to the right screen.
5. Open Settings from a document, click Back, and confirm you return to that document.
6. Open Settings again, press Escape outside a text field, and confirm Settings closes.
7. Visit ?p=/import, ?p=/published, and ?p=/settings and confirm each redirects to the new Settings route.

Screen recording

Grabacion.de.pantalla.2026-07-07.a.las.12.21.13.mov