feat: add public-facing web interface with domain-based routing

Add public-web service with static landing page for client enrollment and device provisioning. Add public-web container to docker-compose with port 8082. Configure nginx reverse proxy with domain-based routing: admin-vpn.nesterovic.cc for admin interface and vpn.nesterovic.cc for public interface. Add proxy headers for X-Real-IP, X-Forwarded-For and X-Forwarded-Proto to both server blocks. Create public-web Dockerfile with nginx serving

public-web/nginx.conf

@@ -0,0 +1,10 @@
+server {
+    listen 80;
+    server_name _;
+    root /usr/share/nginx/html;
+    index index.html;
+
+    location / {
+        try_files $uri /index.html;
+    }
+}