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/api/handlers.go

@@ -22,7 +22,6 @@ import (
 	"github.com/insertr/insertr/internal/engine"
 )
 
-
 // ContentHandler handles all content-related HTTP requests
 type ContentHandler struct {
 	database    *db.Database
@@ -1094,7 +1093,7 @@ func (h *ContentHandler) UpdateCollectionItem(w http.ResponseWriter, r *http.Req
 				maxPos = 0
 			}
 		}
-		
+
 		// Check if position is valid (1-based, within bounds)
 		if int64(req.Position) > maxPos {
 			http.Error(w, fmt.Sprintf("Invalid position: %d exceeds max position %d", req.Position, maxPos), http.StatusBadRequest)
@@ -1117,7 +1116,7 @@ func (h *ContentHandler) UpdateCollectionItem(w http.ResponseWriter, r *http.Req
 				return
 			}
 		}
-		
+
 		// If only position update (no html_content), just get the updated item
 		if req.HTMLContent == "" {
 			updatedItem, err = h.database.GetSQLiteQueries().GetCollectionItem(context.Background(), sqlite.GetCollectionItemParams{
@@ -1149,7 +1148,7 @@ func (h *ContentHandler) UpdateCollectionItem(w http.ResponseWriter, r *http.Req
 				return
 			}
 		}
-		
+
 		// If only position update (no html_content), just get the updated item
 		if req.HTMLContent == "" {
 			updatedItem, err = h.database.GetPostgreSQLQueries().GetCollectionItem(context.Background(), postgresql.GetCollectionItemParams{
@@ -1226,6 +1225,112 @@ func (h *ContentHandler) DeleteCollectionItem(w http.ResponseWriter, r *http.Req
 	w.WriteHeader(http.StatusNoContent)
 }
 
+// ReorderCollection handles PUT /api/collections/{id}/reorder
+func (h *ContentHandler) ReorderCollection(w http.ResponseWriter, r *http.Request) {
+	collectionID := chi.URLParam(r, "id")
+	siteID := r.URL.Query().Get("site_id")
+
+	if siteID == "" {
+		http.Error(w, "site_id parameter is required", http.StatusBadRequest)
+		return
+	}
+
+	var req ReorderCollectionRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		http.Error(w, "Invalid JSON", http.StatusBadRequest)
+		return
+	}
+
+	if req.UpdatedBy == "" {
+		req.UpdatedBy = "api"
+	}
+
+	// Validate that all items belong to the collection and have valid positions
+	if len(req.Items) == 0 {
+		http.Error(w, "Items array cannot be empty", http.StatusBadRequest)
+		return
+	}
+
+	// Update positions for all items in a transaction for atomicity
+	switch h.database.GetDBType() {
+	case "sqlite3":
+		// Use transaction for atomic bulk updates
+		tx, err := h.database.GetSQLiteDB().Begin()
+		if err != nil {
+			http.Error(w, "Failed to begin transaction", http.StatusInternalServerError)
+			return
+		}
+		defer tx.Rollback()
+
+		// Create queries with transaction context
+		qtx := h.database.GetSQLiteQueries().WithTx(tx)
+
+		for _, item := range req.Items {
+			err = qtx.UpdateCollectionItemPosition(context.Background(), sqlite.UpdateCollectionItemPositionParams{
+				ItemID:       item.ItemID,
+				CollectionID: collectionID,
+				SiteID:       siteID,
+				Position:     int64(item.Position),
+				LastEditedBy: req.UpdatedBy,
+			})
+			if err != nil {
+				http.Error(w, fmt.Sprintf("Failed to update position for item %s: %v", item.ItemID, err), http.StatusInternalServerError)
+				return
+			}
+		}
+
+		// Commit transaction
+		if err = tx.Commit(); err != nil {
+			http.Error(w, "Failed to commit bulk reorder transaction", http.StatusInternalServerError)
+			return
+		}
+
+	case "postgres":
+		// Use transaction for atomic bulk updates
+		tx, err := h.database.GetPostgreSQLDB().Begin()
+		if err != nil {
+			http.Error(w, "Failed to begin transaction", http.StatusInternalServerError)
+			return
+		}
+		defer tx.Rollback()
+
+		// Create queries with transaction context
+		qtx := h.database.GetPostgreSQLQueries().WithTx(tx)
+
+		for _, item := range req.Items {
+			err = qtx.UpdateCollectionItemPosition(context.Background(), postgresql.UpdateCollectionItemPositionParams{
+				ItemID:       item.ItemID,
+				CollectionID: collectionID,
+				SiteID:       siteID,
+				Position:     int32(item.Position),
+				LastEditedBy: req.UpdatedBy,
+			})
+			if err != nil {
+				http.Error(w, fmt.Sprintf("Failed to update position for item %s: %v", item.ItemID, err), http.StatusInternalServerError)
+				return
+			}
+		}
+
+		// Commit transaction
+		if err = tx.Commit(); err != nil {
+			http.Error(w, "Failed to commit bulk reorder transaction", http.StatusInternalServerError)
+			return
+		}
+
+	default:
+		http.Error(w, "Unsupported database type", http.StatusInternalServerError)
+		return
+	}
+
+	// Return success response
+	w.Header().Set("Content-Type", "application/json")
+	response := map[string]interface{}{
+		"success": true,
+		"message": fmt.Sprintf("Successfully reordered %d items", len(req.Items)),
+	}
+	json.NewEncoder(w).Encode(response)
+}
+
 // Collection conversion helpers
 
 // convertToAPICollection converts database collection to API model