feat: implement unified content engine to eliminate ID generation inconsistencies

- Create internal/engine module as single source of truth for content processing
- Consolidate 4 separate ID generation systems into one unified engine
- Update API handlers to use engine for consistent server-side ID generation
- Remove frontend client-side ID generation, delegate to server engine
- Ensure identical HTML markup + file path produces identical content IDs
- Resolve content persistence failures caused by ID fragmentation between manual editing and enhancement processes

internal/api/handlers.go

@@ -19,8 +19,7 @@ import (
 	"github.com/insertr/insertr/internal/db"
 	"github.com/insertr/insertr/internal/db/postgresql"
 	"github.com/insertr/insertr/internal/db/sqlite"
-	"github.com/insertr/insertr/internal/parser"
-	"golang.org/x/net/html"
+	"github.com/insertr/insertr/internal/engine"
 )
 
 // ContentHandler handles all content-related HTTP requests
@@ -28,14 +27,19 @@ type ContentHandler struct {
 	database    *db.Database
 	authService *auth.AuthService
 	siteManager *content.SiteManager
+	engine      *engine.ContentEngine
 }
 
 // NewContentHandler creates a new content handler
 func NewContentHandler(database *db.Database, authService *auth.AuthService) *ContentHandler {
+	// Create database client for engine
+	dbClient := engine.NewDatabaseClient(database)
+
 	return &ContentHandler{
 		database:    database,
 		authService: authService,
 		siteManager: nil, // Will be set via SetSiteManager
+		engine:      engine.NewContentEngine(dbClient),
 	}
 }
 
@@ -236,16 +240,31 @@ func (h *ContentHandler) CreateContent(w http.ResponseWriter, r *http.Request) {
 		siteID = "default" // final fallback
 	}
 
-	// Determine content ID - use provided ID or generate from element context
-	contentID := req.ID
-	if contentID == "" {
-		if req.ElementContext == nil {
-			http.Error(w, "Either ID or element_context required", http.StatusBadRequest)
-			return
-		}
-		contentID = h.generateContentID(req.ElementContext)
+	// Generate content ID using the unified engine
+	if req.HTMLMarkup == "" {
+		http.Error(w, "html_markup is required", http.StatusBadRequest)
+		return
 	}
 
+	result, engineErr := h.engine.ProcessContent(engine.ContentInput{
+		HTML:     []byte(req.HTMLMarkup),
+		FilePath: req.FilePath,
+		SiteID:   siteID,
+		Mode:     engine.IDGeneration,
+	})
+	if engineErr != nil {
+		http.Error(w, fmt.Sprintf("ID generation failed: %v", engineErr), http.StatusInternalServerError)
+		return
+	}
+
+	if len(result.Elements) == 0 {
+		http.Error(w, "No insertr elements found in HTML markup", http.StatusBadRequest)
+		return
+	}
+
+	// Use the ID generated by the engine for the first element
+	contentID := result.Elements[0].ID
+
 	// Extract user from request using authentication service
 	userInfo, authErr := h.authService.ExtractUserFromRequest(r)
 	if authErr != nil {
@@ -681,44 +700,7 @@ func (h *ContentHandler) versionMatches(version interface{}, contentID, siteID s
 	return false
 }
 
-// generateContentID creates a content ID from element context using the parser
-func (h *ContentHandler) generateContentID(ctx *ElementContext) string {
-	// Create virtual node for existing parser ID generation
-	virtualNode := &html.Node{
-		Type: html.ElementNode,
-		Data: ctx.Tag,
-		Attr: []html.Attribute{
-			{Key: "class", Val: strings.Join(ctx.Classes, " ")},
-		},
-	}
-
-	// Add parent context as a virtual parent node if provided
-	if ctx.ParentContext != "" && ctx.ParentContext != "content" {
-		parentNode := &html.Node{
-			Type: html.ElementNode,
-			Data: "section",
-			Attr: []html.Attribute{
-				{Key: "class", Val: ctx.ParentContext},
-			},
-		}
-		parentNode.AppendChild(virtualNode)
-		virtualNode.Parent = parentNode
-	}
-
-	// Add text content for hash generation
-	if ctx.OriginalContent != "" {
-		textNode := &html.Node{
-			Type: html.TextNode,
-			Data: ctx.OriginalContent,
-		}
-		virtualNode.AppendChild(textNode)
-	}
-
-	// Use existing parser ID generator
-	// For API-generated IDs, use a placeholder filePath since we don't have file context
-	idGenerator := parser.NewIDGenerator()
-	return idGenerator.Generate(virtualNode, "api-generated")
-}
+// generateContentID function removed - using unified ContentEngine instead
 
 // ServeInsertrJS handles GET /insertr.js - serves the insertr JavaScript library
 func (h *ContentHandler) ServeInsertrJS(w http.ResponseWriter, r *http.Request) {

internal/api/models.go

@@ -42,12 +42,12 @@ type ElementContext struct {
 
 // Request models
 type CreateContentRequest struct {
-	ID             string          `json:"id,omitempty"`              // For enhanced sites
-	ElementContext *ElementContext `json:"element_context,omitempty"` // For non-enhanced sites
-	SiteID         string          `json:"site_id,omitempty"`
-	Value          string          `json:"value"`
-	Type           string          `json:"type"`
-	CreatedBy      string          `json:"created_by,omitempty"`
+	HTMLMarkup string `json:"html_markup"`          // HTML markup of the element
+	FilePath   string `json:"file_path"`            // File path for consistent ID generation
+	Value      string `json:"value"`                // Content value
+	Type       string `json:"type"`                 // Content type
+	SiteID     string `json:"site_id,omitempty"`    // Site identifier
+	CreatedBy  string `json:"created_by,omitempty"` // User who created the content
 }
 
 type RollbackContentRequest struct {