[FEATURE] Make Langfuse TraceUrl accessible from Custom JS and Custom Tool nodes

[dkindlund]

Describe the feature you'd like When Langfuse analytics are enabled, a TraceUrl is assigned by Langfuse for each LLM call. It would be wonderful if there were a way to access that TraceUrl from within Custom JS and Custom Tool nodes, so that we can use it for additional processing.

Additional context Ref: https://langfuse.com/docs/tracing

// trace object
trace.getTraceUrl()

// Langchain callback handler
handler.getTraceUrl();

Maybe this is already accessible and I just don't know where to look @HenryHengZJ -- @marcklingen any tips you have here could also be useful. Thanks!