feat: implement full authentication system with CSRF protection and email verification flow

lib/sanitize.ts

@@ -0,0 +1,17 @@
+import DOMPurify from 'isomorphic-dompurify';
+
+/**
+ * Sanitizes HTML content to prevent XSS attacks.
+ * Use this before passing content to dangerouslySetInnerHTML.
+ */
+export function sanitizeHTML(html: string): string {
+    return DOMPurify.sanitize(html, {
+        USE_PROFILES: { html: true },
+        ALLOWED_TAGS: [
+            'p', 'br', 'b', 'i', 'em', 'strong', 'a', 'ul', 'ol', 'li', 
+            'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'blockquote', 'span', 'div',
+            'img', 'table', 'thead', 'tbody', 'tr', 'th', 'td'
+        ],
+        ALLOWED_ATTR: ['href', 'target', 'rel', 'src', 'alt', 'class', 'style']
+    });
+}