Add nginx reverse proxy for /api and /health to backend server

The frontend builds with VITE_API_URL=/api so all API calls target
the same origin. Without a proxy rule, nginx was serving index.html
for API paths, causing JSON parse errors.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/nginx.conf

@@ -3,6 +3,17 @@ server {
     root /usr/share/nginx/html;
     index index.html;
 
+    location /api/ {
+        proxy_pass http://server:3001;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    }
+
+    location /health {
+        proxy_pass http://server:3001;
+    }
+
     location / {
         try_files $uri $uri/ /index.html;
     }