feat: Complete HTML-first architecture implementation with API integration

- Replace value field with html_content for direct HTML storage
- Add original_template field for style detection preservation
- Remove all markdown processing from injector (delete markdown.go)
- Fix critical content extraction/injection bugs in engine
- Add missing UpdateContent PUT handler for content persistence
- Fix API client field names and add updateContent() method
- Resolve content type validation (only allow text/link types)
- Add UUID-based ID generation to prevent collisions
- Complete first-pass processing workflow for unprocessed elements
- Verify end-to-end: Enhancement → Database → API → Editor → Persistence

All 37 files updated for HTML-first content management system.
Phase 3a implementation complete and production ready.

internal/content/database.go

@@ -12,6 +12,14 @@ import (
 	"github.com/insertr/insertr/internal/engine"
 )
 
+// Helper function to convert sql.NullString to string
+func getStringFromNullString(ns sql.NullString) string {
+	if ns.Valid {
+		return ns.String
+	}
+	return ""
+}
+
 // DatabaseClient implements ContentClient for direct database access
 type DatabaseClient struct {
 	db *db.Database
@@ -132,20 +140,22 @@ func (d *DatabaseClient) convertToContentItem(content interface{}) engine.Conten
 	case "sqlite3":
 		c := content.(sqlite.Content)
 		return engine.ContentItem{
-			ID:        c.ID,
-			SiteID:    c.SiteID,
-			Value:     c.Value,
-			Type:      c.Type,
-			UpdatedAt: time.Unix(c.UpdatedAt, 0).Format(time.RFC3339),
+			ID:               c.ID,
+			SiteID:           c.SiteID,
+			HTMLContent:      c.HtmlContent,
+			OriginalTemplate: getStringFromNullString(c.OriginalTemplate),
+			Type:             c.Type,
+			UpdatedAt:        time.Unix(c.UpdatedAt, 0).Format(time.RFC3339),
 		}
 	case "postgresql":
 		c := content.(postgresql.Content)
 		return engine.ContentItem{
-			ID:        c.ID,
-			SiteID:    c.SiteID,
-			Value:     c.Value,
-			Type:      c.Type,
-			UpdatedAt: time.Unix(c.UpdatedAt, 0).Format(time.RFC3339),
+			ID:               c.ID,
+			SiteID:           c.SiteID,
+			HTMLContent:      c.HtmlContent,
+			OriginalTemplate: getStringFromNullString(c.OriginalTemplate),
+			Type:             c.Type,
+			UpdatedAt:        time.Unix(c.UpdatedAt, 0).Format(time.RFC3339),
 		}
 	}
 	return engine.ContentItem{} // Should never happen
@@ -171,3 +181,61 @@ func (d *DatabaseClient) convertToContentItemList(contentList interface{}) []eng
 	}
 	return []engine.ContentItem{} // Should never happen
 }
+
+// CreateContent creates a new content item  
+func (c *DatabaseClient) CreateContent(siteID, contentID, htmlContent, originalTemplate, contentType, lastEditedBy string) (*engine.ContentItem, error) {
+	switch c.db.GetDBType() {
+	case "sqlite3":
+		content, err := c.db.GetSQLiteQueries().CreateContent(context.Background(), sqlite.CreateContentParams{
+			ID:               contentID,
+			SiteID:           siteID,
+			HtmlContent:      htmlContent,
+			OriginalTemplate: toNullString(originalTemplate),
+			Type:             contentType,
+			LastEditedBy:     lastEditedBy,
+		})
+		if err != nil {
+			return nil, err
+		}
+		return &engine.ContentItem{
+			ID:               content.ID,
+			SiteID:           content.SiteID,
+			HTMLContent:      content.HtmlContent,
+			OriginalTemplate: getStringFromNullString(content.OriginalTemplate),
+			Type:             content.Type,
+			LastEditedBy:     content.LastEditedBy,
+		}, nil
+
+	case "postgresql":
+		content, err := c.db.GetPostgreSQLQueries().CreateContent(context.Background(), postgresql.CreateContentParams{
+			ID:               contentID,
+			SiteID:           siteID,
+			HtmlContent:      htmlContent,
+			OriginalTemplate: toNullString(originalTemplate),
+			Type:             contentType,
+			LastEditedBy:     lastEditedBy,
+		})
+		if err != nil {
+			return nil, err
+		}
+		return &engine.ContentItem{
+			ID:               content.ID,
+			SiteID:           content.SiteID,
+			HTMLContent:      content.HtmlContent,
+			OriginalTemplate: getStringFromNullString(content.OriginalTemplate),
+			Type:             content.Type,
+			LastEditedBy:     content.LastEditedBy,
+		}, nil
+
+	default:
+		return nil, fmt.Errorf("unsupported database type: %s", c.db.GetDBType())
+	}
+}
+
+// Helper function to convert string to sql.NullString
+func toNullString(s string) sql.NullString {
+	if s == "" {
+		return sql.NullString{Valid: false}
+	}
+	return sql.NullString{String: s, Valid: true}
+}