Feat: Limit the iteration start node to only be the source node #4242 (#4260)

### What problem does this PR solve?

Feat: Limit the iteration start node to only be the source node #4242

### Type of change


- [x] New Feature (non-breaking change which adds functionality)

web/src/pages/flow/canvas/edge/index.tsx

@@ -44,8 +44,6 @@ export function ButtonEdge({
   };
 
   // highlight the nodes that the workflow passes through
-  // const queryClient = useQueryClient();
-  // const flowDetail = queryClient.getQueryData<IFlow>(['flowDetail']);
   const { data: flowDetail } = useFetchFlow();
 
   const graphPath = useMemo(() => {

web/src/pages/flow/canvas/node/iteration-node.tsx

@@ -109,6 +109,7 @@ export function IterationStartNode({
         isConnectable={isConnectable}
         className={styles.handle}
         style={RightHandleStyle}
+        isConnectableEnd={false}
       ></Handle>
       <div>
         <ListRestart className="size-7" />