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/engine/database_client.go

@@ -0,0 +1,112 @@
+package engine
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/insertr/insertr/internal/db"
+	"github.com/insertr/insertr/internal/db/postgresql"
+	"github.com/insertr/insertr/internal/db/sqlite"
+)
+
+// DatabaseClient implements ContentClient interface using the database
+type DatabaseClient struct {
+	database *db.Database
+}
+
+// NewDatabaseClient creates a new database client
+func NewDatabaseClient(database *db.Database) *DatabaseClient {
+	return &DatabaseClient{
+		database: database,
+	}
+}
+
+// GetContent retrieves a single content item
+func (c *DatabaseClient) GetContent(siteID, contentID string) (*ContentItem, error) {
+	switch c.database.GetDBType() {
+	case "sqlite3":
+		content, err := c.database.GetSQLiteQueries().GetContent(context.Background(), sqlite.GetContentParams{
+			ID:     contentID,
+			SiteID: siteID,
+		})
+		if err != nil {
+			return nil, err
+		}
+		return &ContentItem{
+			ID:           content.ID,
+			SiteID:       content.SiteID,
+			Value:        content.Value,
+			Type:         content.Type,
+			LastEditedBy: content.LastEditedBy,
+		}, nil
+
+	case "postgresql":
+		content, err := c.database.GetPostgreSQLQueries().GetContent(context.Background(), postgresql.GetContentParams{
+			ID:     contentID,
+			SiteID: siteID,
+		})
+		if err != nil {
+			return nil, err
+		}
+		return &ContentItem{
+			ID:           content.ID,
+			SiteID:       content.SiteID,
+			Value:        content.Value,
+			Type:         content.Type,
+			LastEditedBy: content.LastEditedBy,
+		}, nil
+
+	default:
+		return nil, fmt.Errorf("unsupported database type: %s", c.database.GetDBType())
+	}
+}
+
+// GetBulkContent retrieves multiple content items
+func (c *DatabaseClient) GetBulkContent(siteID string, contentIDs []string) ([]*ContentItem, error) {
+	switch c.database.GetDBType() {
+	case "sqlite3":
+		contents, err := c.database.GetSQLiteQueries().GetBulkContent(context.Background(), sqlite.GetBulkContentParams{
+			SiteID: siteID,
+			Ids:    contentIDs,
+		})
+		if err != nil {
+			return nil, err
+		}
+
+		items := make([]*ContentItem, len(contents))
+		for i, content := range contents {
+			items[i] = &ContentItem{
+				ID:           content.ID,
+				SiteID:       content.SiteID,
+				Value:        content.Value,
+				Type:         content.Type,
+				LastEditedBy: content.LastEditedBy,
+			}
+		}
+		return items, nil
+
+	case "postgresql":
+		contents, err := c.database.GetPostgreSQLQueries().GetBulkContent(context.Background(), postgresql.GetBulkContentParams{
+			SiteID: siteID,
+			Ids:    contentIDs,
+		})
+		if err != nil {
+			return nil, err
+		}
+
+		items := make([]*ContentItem, len(contents))
+		for i, content := range contents {
+			items[i] = &ContentItem{
+				ID:           content.ID,
+				SiteID:       content.SiteID,
+				Value:        content.Value,
+				Type:         content.Type,
+				LastEditedBy: content.LastEditedBy,
+			}
+		}
+		return items, nil
+
+	default:
+		return nil, fmt.Errorf("unsupported database type: %s", c.database.GetDBType())
+	}
+}