Best-effort file:line of the application frame that issued a span, so the dashboard can point at the line that ran a query / HTTP call.

Walks the current process stacktrace and returns the first frame that belongs to the host application — skipping the SDK itself, the standard library, and known instrumentation/driver dependencies (Ecto, Phoenix, Plug, Finch, Tesla, Postgrex, DBConnection, …). Returns nil rather than throwing.