update layouts

apps/admin/src/app/layouts/01__Default/README.md

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+# Default layout
+
+**Metronic 9 reference:** [Demo 1](https://keenthemes.com/metronic/tailwind/react/demo1)
+
+A fixed sidebar carrying the application menu next to a fixed header. The sidebar can be collapsed
+to icons, and the choice is remembered in settings under
+`layouts.default-layout.sidebarCollapse`. Below `lg` the sidebar moves into a sheet opened from the
+header.
+
+## Composition
+
+| Piece                   | Source                                        |
+| ----------------------- | --------------------------------------------- |
+| Sidebar menu            | `SidebarAccordionMenu` from `../shared`       |
+| Toolbar and breadcrumbs | `Toolbar` / `ToolbarHeading` from `../shared` |
+| Footer                  | `AppFooter` from `../shared`                  |
+| Account menu            | `UserAvatarMenu` from `../shared`             |
+
+Layout-specific: `Sidebar`, `SidebarHeader` (logo plus the collapse toggle), `Header`.
+
+## Notes
+
+- Body classes `sidebar-fixed`, `header-fixed` and `layout-initialized` are added on mount and
+  removed on unmount, so switching to another layout leaves no styling behind.