fix: use relative API URLs and allow any LAN IP for CORS

nginx.conf

@@ -0,0 +1,32 @@
+server {
+    listen 80;
+    server_name _;
+
+    # API requests → backend
+    location /api/ {
+        proxy_pass http://localhost:5000;
+        proxy_http_version 1.1;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    }
+
+    # Socket.IO → backend (WebSocket upgrade)
+    location /socket.io/ {
+        proxy_pass http://localhost:5000;
+        proxy_http_version 1.1;
+        proxy_set_header Upgrade $http_upgrade;
+        proxy_set_header Connection "upgrade";
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+    }
+
+    # Everything else → Vite dev server
+    location / {
+        proxy_pass http://localhost:3000;
+        proxy_http_version 1.1;
+        proxy_set_header Upgrade $http_upgrade;
+        proxy_set_header Connection "upgrade";
+        proxy_set_header Host $host;
+    }
+}