fix: nginx reverse proxy for API/wizard, fix Object.entries null crash

- Replace serve with nginx for proper reverse proxy
- /api/* proxied to backend:8000, /wizard/* proxied to wizard:8080
- Eliminates CORS issues (same-origin requests)
- Fixes SPA fallback returning 200 for API routes (was hiding backend-down state)
- Add null guards on Object.entries for dashboard stats
- Remove VITE_API_BASE/VITE_WIZARD_PORT build args (no longer needed)

nginx.conf

@@ -0,0 +1,29 @@
+server {
+    listen 3000;
+    root /usr/share/nginx/html;
+    index index.html;
+
+    # Backend API proxy
+    location /api/ {
+        proxy_pass http://backend:8000/;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_connect_timeout 5s;
+        proxy_read_timeout 30s;
+    }
+
+    # Wizard API proxy (setup phase only)
+    location /wizard/ {
+        proxy_pass http://wizard:8080/;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_connect_timeout 5s;
+        proxy_read_timeout 10s;
+    }
+
+    # SPA fallback — only for non-API, non-asset routes
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+}