feat(home): landscape-phone layout — horizontal carousel of compact cards

When the PWA is rotated on a phone, vertical space is too tight for the
full-bleed vertical stack. Detect landscape phones via
@media (orientation: landscape) and (max-height: 600px) and:

- Flip the stack to a horizontal scroll-snap carousel
- Shrink each slide to min(320px, 70vw) so 2-3 cards are visible at a time
- Restructure the card body to a single row: name + status on the left,
  Add button on the right; sync line is dropped to keep things tight
- Constrain the photo to fill card height (object-fit: contain) instead
  of card width, so it never overflows the short viewport

Manifest also updated to orientation: any so iOS doesn't lock the
standalone PWA back to portrait.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/public/manifest.webmanifest

@@ -6,7 +6,7 @@
   "start_url": "/",
   "scope": "/",
   "display": "standalone",
-  "orientation": "portrait",
+  "orientation": "any",
   "background_color": "#fdf6ee",
   "theme_color": "#fdf6ee",
   "icons": [