feat: complete nginx migration from caddy

- Replace Caddy reverse proxy with Nginx (nginx:alpine)
- Add nginx.conf with HTTP/HTTPS, gzip, and proxy settings
- Add nginx-custom-domains.conf template for custom domains
- Update docker-compose.yml to use Nginx service
- Add ProxyFix middleware to Flask app for proper header handling
- Create nginx_config_reader.py utility to read Nginx configuration
- Update admin blueprint to display Nginx status in https_config page
- Add Nginx configuration display to https_config.html template
- Generate self-signed SSL certificates for localhost
- Add utility scripts: generate_nginx_certs.sh
- Add documentation: NGINX_SETUP_QUICK.md, PROXY_FIX_SETUP.md
- All containers now running, HTTPS working, HTTP redirects to HTTPS
- Session cookies marked as Secure
- Security headers properly configured

generate_nginx_certs.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+# Generate self-signed SSL certificates for Nginx
+# Usage: ./generate_nginx_certs.sh [domain] [days]
+
+DOMAIN=${1:-localhost}
+DAYS=${2:-365}
+CERT_DIR="./data/nginx-ssl"
+
+echo "🔐 Generating self-signed SSL certificate for Nginx"
+echo "Domain: $DOMAIN"
+echo "Valid for: $DAYS days"
+echo "Certificate directory: $CERT_DIR"
+
+# Create directory if it doesnt exist
+mkdir -p "$CERT_DIR"
+
+# Generate private key and certificate
+openssl req -x509 -nodes -days "$DAYS" \
+    -newkey rsa:2048 \
+    -keyout "$CERT_DIR/key.pem" \
+    -out "$CERT_DIR/cert.pem" \
+    -subj "/CN=$DOMAIN/O=DigiServer/C=US"
+
+# Set proper permissions
+chmod 644 "$CERT_DIR/cert.pem"
+chmod 600 "$CERT_DIR/key.pem"
+
+echo "✅ Certificates generated successfully!"
+echo "Certificate: $CERT_DIR/cert.pem"
+echo "Key: $CERT_DIR/key.pem"