feat: visual polish & UX — fade-in, theme toggle, scroll-to-top, footer, cursor, badge

- Add FadeIn component (IntersectionObserver scroll-reveal + load animation)
- Add dark/light theme toggle (useSyncExternalStore + localStorage)
- Add scroll-to-top button (appears after 300px scroll)
- Add configurable footer with social links (gallery.yaml)
- Add crosshair cursor on photo grid items
- Add 'X photos' count badge on subpage cover images
- Add light theme color palette in tokens.css

docker-compose.yml

@@ -4,7 +4,7 @@ services:
     container_name: immich-lightbox
     restart: unless-stopped
     ports:
-      - "7211:7211"
+      - '7211:7211'
     env_file:
       - .env.local
     volumes: