Implement auto-generation of ecosystem.config.js and improve container setup

- Add automatic ecosystem.config.js generation from package.json
- Create app directory automatically if missing
- Copy simple-website example when app directory is empty
- Remove redundant default app files from configs/
- Add HAProxy support with proper real IP forwarding
- Configure nginx to trust proxy headers from private networks
- Simplify entrypoint logic - always use /home/$user/app

This makes the container more user-friendly by eliminating the need for
manual PM2 configuration and ensuring the server always has a working app.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

configs/nginx.conf

@@ -17,6 +17,14 @@ http {
     client_max_body_size 8m;
     large_client_header_buffers 2 1k;
     
+    # Real IP configuration for HAProxy
+    set_real_ip_from 10.0.0.0/8;     # Private network range
+    set_real_ip_from 172.16.0.0/12;  # Private network range
+    set_real_ip_from 192.168.0.0/16; # Private network range
+    set_real_ip_from 127.0.0.1;      # Localhost
+    real_ip_header X-Forwarded-For;
+    real_ip_recursive on;
+    
     log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                       '$status $body_bytes_sent "$http_referer" '
                       '"$http_user_agent" "$http_x_forwarded_for"';