security: add security headers to nginx config to prevent XSS, clickjacking and enforce HTTPS

nginx.conf

@@ -5,6 +5,28 @@ server {
     root /usr/share/nginx/html;
     index index.html index.htm;
 
+    # Security Headers
+    # Content Security Policy (CSP) - Prevents XSS attacks
+    add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; font-src 'self'; connect-src 'self'; frame-ancestors 'none';" always;
+    
+    # Strict Transport Security (HSTS) - Forces HTTPS
+    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;
+    
+    # X-Frame-Options - Prevents clickjacking
+    add_header X-Frame-Options "DENY" always;
+    
+    # X-Content-Type-Options - Prevents MIME type sniffing
+    add_header X-Content-Type-Options "nosniff" always;
+    
+    # Referrer Policy - Controls referrer information
+    add_header Referrer-Policy "strict-origin-when-cross-origin" always;
+    
+    # X-XSS-Protection - Additional XSS protection (legacy but still useful)
+    add_header X-XSS-Protection "1; mode=block" always;
+    
+    # Permissions Policy - Controls browser features
+    add_header Permissions-Policy "geolocation=(), microphone=(), camera=()" always;
+
     location / {
         try_files $uri $uri/ /index.html;
     }