fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE318-EXPAT-6446356

Dockerfile

@@ -1,5 +1,5 @@
 # Use the Nginx image from Docker Hub
-FROM nginx:alpine
+FROM nginx:1.25.4-alpine3.18
 
 # Copy the HTML file to the Nginx document root
 COPY index.html /usr/share/nginx/html