Add /set: on-set screen tracking markers for crews

- Unlinked, noindex page listing marker PNGs from public/set/markers
  (discovered at build time; filenames encode device/resolution/orientation)
- Detects the current screen and offers the closest match first
- One-tap full-screen viewer: wake lock, hidden controls, full grid/edges
  toggle, fill vs fit by aspect, back button closes, deep links via hash
- Offline service worker + home-screen manifest for iPhone full screen
- Marketing chrome moved into an (site) route group so /set has none

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docker/nginx.conf

@@ -23,6 +23,16 @@ server {
         add_header Cache-Control "public, max-age=604800";
     }
 
+    # Offline worker for /set must always be revalidated so updates roll out
+    location = /set/sw.js {
+        add_header Cache-Control "no-cache";
+    }
+
+    location ~* \.webmanifest$ {
+        types { application/manifest+json webmanifest; }
+        add_header Cache-Control "no-cache";
+    }
+
     error_page 404 /404.html;
 
     gzip on;