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>

scripts/create-nginx-config.sh

@@ -35,7 +35,8 @@ server {
         proxy_set_header Host \$host;
         proxy_set_header X-Real-IP \$remote_addr;
         proxy_set_header X-Forwarded-For \$proxy_add_x_forwarded_for;
-        proxy_set_header X-Forwarded-Proto \$scheme;
+        proxy_set_header X-Forwarded-Proto \$http_x_forwarded_proto;
+        proxy_set_header X-CLIENT-IP \$http_x_client_ip;
         proxy_cache_bypass \$http_upgrade;
     }