Clean up codebase: remove unused demos and test files

- Remove dan-eden-portfolio and devigo-web demo sites
- Clean up demo testing infrastructure and scripts
- Remove frontend test files (html-preservation, style-detection tests)
- Update configuration and auth improvements
- Simplify demo structure to focus on core functionality

This cleanup reduces repository size and focuses on essential demos.

internal/engine/utils.go

@@ -4,6 +4,7 @@ import (
 	"strings"
 
 	"golang.org/x/net/html"
+	"slices"
 )
 
 // GetClasses extracts CSS classes from an HTML node
@@ -19,12 +20,7 @@ func GetClasses(node *html.Node) []string {
 
 // ContainsClass checks if a class list contains a specific class
 func ContainsClass(classes []string, target string) bool {
-	for _, class := range classes {
-		if class == target {
-			return true
-		}
-	}
-	return false
+	return slices.Contains(classes, target)
 }
 
 // getAttribute gets an attribute value from an HTML node
@@ -37,29 +33,6 @@ func getAttribute(node *html.Node, key string) string {
 	return ""
 }
 
-// hasOnlyTextContent checks if a node contains only text content (no nested HTML elements)
-// DEPRECATED: Use hasEditableContent for more sophisticated detection
-func hasOnlyTextContent(node *html.Node) bool {
-	if node.Type != html.ElementNode {
-		return false
-	}
-
-	for child := node.FirstChild; child != nil; child = child.NextSibling {
-		switch child.Type {
-		case html.ElementNode:
-			// Found a nested HTML element - not text-only
-			return false
-		case html.TextNode:
-			// Text nodes are fine, continue checking
-			continue
-		default:
-			// Comments, etc. - continue checking
-			continue
-		}
-	}
-	return true
-}
-
 // Inline formatting elements that are safe for editing
 var inlineFormattingTags = map[string]bool{
 	"strong": true,