feat(core): app menu waffle launcher

- Popover grid replaces the old hamburger overlay
- Roving tabindex keyboard nav (arrow keys, Home/End, Enter/Space)
- Focus returns to whichever trigger opened the popover
- RTL-aware horizontal alignment
- Admin-only "More apps" tile
- Unit + Cypress coverage

Resolves: #59888
Signed-off-by: Peter Ringelmann <peter.ringelmann@nextcloud.com>

Author: pringelmann

core/css/header.css

@@ -84,7 +84,6 @@
 	// focus visible styles
 	// this adds a small line below all entries when visually focussed
 	#nextcloud:focus-visible,
-	.app-menu-entry a:focus-visible,
 	.header-menu button:first-of-type:focus-visible {
 		outline: none;