Curated webhook event types

The canonical list of subscribable event types — the source the portal renders its multi-select from. Pass selected ids as `events` on create/update; the server expands them to channel globs (injecting your orgId for the private `user-trade` type). `matcher` is `stream` or `anomaly`; `highVolume` flags high-rate topics; `orgScoped` marks types whose channel embeds your org (you never type it).