Add photo frame idle mode and switch to Skylight-style theme

- After 5 min of no touch/motion, dashboard hides behind a fullscreen
  photo slideshow with centered time and date overlay
- Photos loaded from PHOTOS_PATH env var (defaults to ~/Pictures/dashboard)
  via IPC + file:// URLs; traversal-guarded, recursive up to 2 levels
- Motion or touch exits idle back to dashboard
- Theme repainted warm cream / sage / stone ink with Nunito font and
  rounded cards; dark tokens kept so component classes still resolve
- Adds PHOTO_FRAME.md with Samba cifs mount + systemd env instructions

src/components/photoframe/index.ts

@@ -0,0 +1 @@
+export { PhotoFrame } from './PhotoFrame';