fix: systematic element matching bug in enhancement pipeline

- Problem: Element ID collisions between similar elements (logo h1 vs hero h1)
  causing content to be injected into wrong elements
- Root cause: Enhancer used naive tag+class matching instead of parser's
  sophisticated semantic analysis for element identification

Systematic solution:
- Enhanced parser architecture with exported utilities (GetClasses, ContainsClass)
- Added FindElementInDocument() with content-based semantic matching
- Replaced naive findAndInjectNodes() with parser-based element matching
- Removed code duplication between parser and enhancer packages

Backend improvements:
- Moved ID generation to backend for single source of truth
- Added ElementContext struct for frontend-backend communication
- Updated API handlers to support context-based content ID generation

Frontend improvements:
- Enhanced getElementMetadata() to extract semantic context
- Updated save flow to handle both enhanced and non-enhanced elements
- Improved API client to use backend-generated content IDs

Result:
- Unique content IDs: navbar-logo-200530 vs hero-title-a1de7b
- Precise element matching using content validation
- Single source of truth for DOM utilities in parser package
- Eliminated 40+ lines of duplicate code while fixing core bug

internal/parser/id_generator.go

@@ -28,7 +28,9 @@ func (g *IDGenerator) Generate(node *html.Node) string {
 	contentHash := g.getContentHash(node)
 
 	baseID := g.createBaseID(context, purpose, contentHash)
-	return g.ensureUnique(baseID)
+	finalID := g.ensureUnique(baseID)
+
+	return finalID
 }
 
 // getSemanticContext determines the semantic context from parent elements
@@ -36,11 +38,11 @@ func (g *IDGenerator) getSemanticContext(node *html.Node) string {
 	// Walk up the tree to find semantic containers
 	parent := node.Parent
 	for parent != nil && parent.Type == html.ElementNode {
-		classes := getClasses(parent)
+		classes := GetClasses(parent)
 
 		// Check for common semantic section classes
 		for _, class := range []string{"hero", "services", "nav", "navbar", "footer", "about", "contact", "testimonial"} {
-			if containsClass(classes, class) {
+			if ContainsClass(classes, class) {
 				return class
 			}
 		}
@@ -68,7 +70,7 @@ func (g *IDGenerator) getSemanticContext(node *html.Node) string {
 // getPurpose determines the purpose/role of the element
 func (g *IDGenerator) getPurpose(node *html.Node) string {
 	tag := strings.ToLower(node.Data)
-	classes := getClasses(node)
+	classes := GetClasses(node)
 
 	// Check for specific CSS classes that indicate purpose
 	for _, class := range classes {

internal/parser/parser.go

@@ -90,15 +90,15 @@ func (p *Parser) parseFile(filePath string) ([]Element, []string, error) {
 // findInsertrElements recursively finds all elements with "insertr" class
 func (p *Parser) findInsertrElements(node *html.Node, filePath string, elements *[]Element, warnings *[]string) {
 	if node.Type == html.ElementNode {
-		classes := getClasses(node)
+		classes := GetClasses(node)
 
 		// Check if element has "insertr" class
-		if containsClass(classes, "insertr") {
+		if ContainsClass(classes, "insertr") {
 			if isContainer(node) {
 				// Container element - expand to viable children
 				viableChildren := findViableChildren(node)
 				for _, child := range viableChildren {
-					childClasses := getClasses(child)
+					childClasses := GetClasses(child)
 					element, warning := p.createElement(child, filePath, childClasses)
 					*elements = append(*elements, element)
 					if warning != "" {
@@ -181,13 +181,13 @@ func (p *Parser) resolveContentID(node *html.Node) (string, bool) {
 // detectContentType determines the content type based on element and classes
 func (p *Parser) detectContentType(node *html.Node, classes []string) ContentType {
 	// Check for explicit type classes first
-	if containsClass(classes, "insertr-markdown") {
+	if ContainsClass(classes, "insertr-markdown") {
 		return ContentMarkdown
 	}
-	if containsClass(classes, "insertr-link") {
+	if ContainsClass(classes, "insertr-link") {
 		return ContentLink
 	}
-	if containsClass(classes, "insertr-text") {
+	if ContainsClass(classes, "insertr-text") {
 		return ContentText
 	}
 

internal/parser/utils.go

@@ -6,8 +6,8 @@ import (
 	"golang.org/x/net/html"
 )
 
-// getClasses extracts CSS classes from an HTML node
-func getClasses(node *html.Node) []string {
+// GetClasses extracts CSS classes from an HTML node
+func GetClasses(node *html.Node) []string {
 	classAttr := getAttribute(node, "class")
 	if classAttr == "" {
 		return []string{}
@@ -17,8 +17,8 @@ func getClasses(node *html.Node) []string {
 	return classes
 }
 
-// containsClass checks if a class list contains a specific class
-func containsClass(classes []string, target string) bool {
+// 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
@@ -157,3 +157,39 @@ func isSelfClosing(node *html.Node) bool {
 
 	return selfClosingTags[node.Data]
 }
+
+// FindElementInDocument finds a parser element in HTML document tree using semantic matching
+func FindElementInDocument(doc *html.Node, element Element) *html.Node {
+	return findElementWithContext(doc, element)
+}
+
+// findElementWithContext uses the parser's semantic understanding to find the correct element
+func findElementWithContext(node *html.Node, target Element) *html.Node {
+	if node.Type == html.ElementNode && node.Data == target.Tag {
+		classes := GetClasses(node)
+		if ContainsClass(classes, "insertr") {
+			// Content-based validation for precise matching
+			textContent := extractTextContent(node)
+			nodeContent := strings.TrimSpace(textContent)
+			targetContent := strings.TrimSpace(target.Content)
+
+			if nodeContent == targetContent {
+				return node
+			}
+		}
+	}
+
+	// Recursively search children
+	for child := node.FirstChild; child != nil; child = child.NextSibling {
+		if result := findElementWithContext(child, target); result != nil {
+			return result
+		}
+	}
+
+	return nil
+}
+
+// GetAttribute gets an attribute value from an HTML node (exported version)
+func GetAttribute(node *html.Node, key string) string {
+	return getAttribute(node, key)
+}