Fix trigger delete: handle 204 No Content in API client

The DELETE /routine-triggers/:id endpoint returns 204 No Content, but
the API client unconditionally called res.json() on all responses,
causing a JSON parse error that surfaced as "API route not found".

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/api/client.ts

@@ -32,6 +32,7 @@ async function request<T>(path: string, init?: RequestInit): Promise<T> {
       errorBody,
     );
   }
+  if (res.status === 204) return undefined as T;
   return res.json();
 }