ListTechEvents retrieves tech events from Techmeme ICS, dev.events RSS, and curated sources.
Event type filter: "all", "conferences", "earnings", "ipo", "other". Empty = all.
Only events with non-virtual coordinates.
Max events to return (0 = unlimited).
Events within N days from now (0 = unlimited).
Successful response
ListTechEventsResponse contains tech events matching the request.
Whether the request succeeded.
Total event count in response.
Number of conference-type events.
Number of mappable (non-virtual with coords) events.
ISO 8601 timestamp of last update.
Error message if success is false.