- Add new `useDeviceSettings` hook (`src/hooks/useDeviceSettings.ts`) to centralize
device-related state:
- exposes `isMobile` and `isPWA`
- supports options: `mobileBreakpoint`, `trackMobile`, `trackPWA`
- listens to window resize for mobile updates
- listens to `display-mode: standalone` changes for PWA updates
- includes `matchMedia.addListener/removeListener` fallback for older environments
- Update `AppContent` (`src/App.jsx`) to consume `isMobile` from
`useDeviceSettings({ trackPWA: false })`:
- remove local `isMobile` state/effect
- remove local `isPWA` state/effect
- keep existing `isMobile` behavior for layout and mobile sidebar flow
- stop passing `isPWA` into `Sidebar` props
- Update `Sidebar` (`src/components/Sidebar.jsx`) to own PWA detection:
- consume `isPWA` from `useDeviceSettings({ trackMobile: false })`
- add effect to toggle `pwa-mode` class on `document.documentElement` and `document.body`
- retain use of `isMobile` prop from `App` for sidebar/mobile rendering decisions
Why:
- removes duplicated device-detection logic from `AppContent`
- makes device-state logic reusable and easier to maintain
- keeps PWA-specific behavior where it is actually used (`Sidebar`)
