Implement collection item reordering with bulk operations and persistent HTML attributes

- Add bulk reorder API endpoint (PUT /api/collections/{id}/reorder) with atomic transactions
- Replace individual position updates with efficient bulk operations in frontend
- Implement unified ID generation and proper data-item-id injection during enhancement
- Fix collection item position persistence through content edit cycles
- Add optimistic UI with rollback capability for better user experience
- Update sqlc queries to include last_edited_by fields in position updates
- Remove obsolete data-content-type attributes and unify naming conventions

internal/engine/injector.go

@@ -162,7 +162,6 @@ func (i *Injector) findElementByTag(node *html.Node, tag string) *html.Node {
 // AddContentAttributes adds necessary data attributes and insertr class for editor functionality
 func (i *Injector) AddContentAttributes(node *html.Node, contentID string, contentType string) {
 	i.setAttribute(node, "data-content-id", contentID)
-	i.setAttribute(node, "data-content-type", contentType)
 	i.addClass(node, "insertr")
 }