Forward real ip in .examples/nginx

Nobody has claimed this yet.

The IP displayed is wrong, because nginx will not send it to php-fpm.
Add this to `.examples/nginx/matomo.conf` on line 24:

```nginx
fastcgi_param REMOTE_ADDR $http_x_real_ip;
```

---

**Side note:**

For the external nginx server (listening to 80/443), one can add:
```nginx
location / {
proxy_pass http://localhost:8080;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Real-IP $remote_addr;
}
```

Open `.examples/nginx/matomo.conf` and inspect the FastCGI parameters around line 24. Update the example so PHP-FPM receives the real client IP, then verify the configuration remains valid and the displayed IP is correct when traffic arrives through the external nginx proxy.

Written by the indexing model from the issue text.