Adds a smoother mobile experience by automatically closing the sidebar
drawer once a menu item is tapped.
### Details
* SiderBar
* Introduce `onNavigate` prop and invoke it on every `<Link>` click.
* Remove unused `useIsMobile` hook and related `isMobile` variable.
* PageLayout
* Pass `onNavigate` callback to `SiderBar` that sets `drawerOpen` to
`false` when on mobile, ensuring the sidebar collapses after
navigation.
This eliminates the “isMobile declared but never used” warning and
aligns the behaviour of the sidebar with common mobile UX expectations.
