Rework the space sidebar:
- remove the "New page" and "Search" menu items (search stays in the app
header; page creation stays via the "+" button in the Pages section)
- move "Space settings" into a gear icon next to the current space name
- drop the searchable space popover and render all spaces as an
always-visible grid of fixed-width cards (icon + name), several per row,
sorted alphabetically, with the active space highlighted
- always inject the active space into the grid so it stays highlightable
even when the user has more than the 100-space API page limit
The shared SpaceSelect component is left untouched (still used by the
move/copy page modals).
a0a7d62b59