Update frontend to use unprivileged Nginx on port 8080

Switch from `nginx:1.29-alpine-slim` to `nginxinc/nginx-unprivileged:stable-alpine` for improved security by running as a non-root user. Changed the exposed port from 80 to 8080 in the configurations to reflect the unprivileged setup. Adjusted the `docker-compose.yml` and `nginx.conf` accordingly.

frontend/nginx.conf

@@ -1,5 +1,5 @@
 server {
-  listen 80;
+  listen 8080;
   server_name _;
 
   root /usr/share/nginx/html;