refactor: see details below

- Fix emailing.
- Updated manage.sh to enhance command handling and service management for backend and frontend.
- Introduced utility functions for better code organization and readability.
- Added support for checking Node.js version and ensuring the virtual environment is set up.
- Implemented improved logging with color-coded output for better visibility.
- Created a new nginx.conf.example file for easy Nginx configuration setup for the application.

nginx.conf.example

@@ -0,0 +1,143 @@
+# ==============================================================================
+# CheckIn App V2 - Nginx Configuration Example (HTTP Only)
+# ==============================================================================
+#
+# Usage:
+#   1. Copy this file: sudo cp nginx.conf.example /etc/nginx/sites-available/checkin-app
+#   2. Edit the file and replace placeholders with your actual values
+#   3. Create symlink: sudo ln -s /etc/nginx/sites-available/checkin-app /etc/nginx/sites-enabled/
+#   4. Test config: sudo nginx -t
+#   5. Reload Nginx: sudo systemctl reload nginx
+#
+# ==============================================================================
+
+# HTTP Server - Production Configuration
+server {
+    listen 80;
+    listen [::]:80;
+    server_name your-domain.com;  # CHANGE THIS: Replace with your domain or IP
+
+    # CHANGE THIS: Replace with your actual frontend build path
+    # Example: /home/username/CheckInApp/frontend/dist
+    root /path/to/CheckInApp/frontend/dist;
+    index index.html;
+
+    # Access and Error Logs
+    access_log /var/log/nginx/checkin-app-access.log;
+    error_log /var/log/nginx/checkin-app-error.log;
+
+    # Gzip Compression
+    gzip on;
+    gzip_vary on;
+    gzip_min_length 1024;
+    gzip_types text/plain text/css text/xml text/javascript
+               application/x-javascript application/xml+rss
+               application/json application/javascript;
+
+    # Client body size (for file uploads)
+    client_max_body_size 10M;
+
+    # ==========================================
+    # API Proxy Configuration
+    # ==========================================
+    location /api/ {
+        # Proxy to backend FastAPI server
+        proxy_pass http://127.0.0.1:8000;
+
+        # Proxy headers
+        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;
+
+        # HTTP version and buffering
+        proxy_http_version 1.1;
+        proxy_buffering off;
+        proxy_request_buffering off;
+
+        # Timeouts
+        proxy_connect_timeout 60s;
+        proxy_send_timeout 60s;
+        proxy_read_timeout 60s;
+    }
+
+    # API Documentation endpoints
+    location ~ ^/(docs|redoc|openapi.json|health) {
+        proxy_pass http://127.0.0.1:8000;
+        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 $scheme;
+    }
+
+    # ==========================================
+    # Frontend Static Files
+    # ==========================================
+
+    # Cache static assets (JS, CSS, images, fonts)
+    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
+        expires 1y;
+        add_header Cache-Control "public, immutable";
+        try_files $uri =404;
+    }
+
+    # Frontend routes (SPA - Single Page Application)
+    location / {
+        try_files $uri $uri/ /index.html;
+        add_header Cache-Control "no-cache, no-store, must-revalidate";
+    }
+
+    # Favicon
+    location = /favicon.ico {
+        log_not_found off;
+        access_log off;
+    }
+
+    # Robots.txt
+    location = /robots.txt {
+        log_not_found off;
+        access_log off;
+    }
+}
+
+# ==============================================================================
+# HTTPS Configuration (Currently Commented Out)
+# ==============================================================================
+# Uncomment and configure below when you need HTTPS with SSL certificate
+#
+# server {
+#     listen 80;
+#     listen [::]:80;
+#     server_name your-domain.com;
+#
+#     # Redirect HTTP to HTTPS
+#     return 301 https://$server_name$request_uri;
+# }
+#
+# server {
+#     listen 443 ssl http2;
+#     listen [::]:443 ssl http2;
+#     server_name your-domain.com;
+#
+#     # SSL Certificate (use Let's Encrypt: certbot --nginx)
+#     ssl_certificate /etc/letsencrypt/live/your-domain.com/fullchain.pem;
+#     ssl_certificate_key /etc/letsencrypt/live/your-domain.com/privkey.pem;
+#
+#     # SSL Configuration
+#     ssl_protocols TLSv1.2 TLSv1.3;
+#     ssl_ciphers 'ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256';
+#     ssl_prefer_server_ciphers off;
+#     ssl_session_cache shared:SSL:10m;
+#     ssl_session_timeout 10m;
+#
+#     # Security Headers
+#     add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
+#     add_header X-Frame-Options "SAMEORIGIN" always;
+#     add_header X-Content-Type-Options "nosniff" always;
+#
+#     # CHANGE THIS: Replace with your actual frontend build path
+#     root /path/to/CheckInApp/frontend/dist;
+#     index index.html;
+#
+#     # ... (rest of the configuration same as HTTP version above)
+# }