fix(web): CronPage crash when rendering schedule object

The cron API returns schedule as {kind, expr, display} object but
CronPage.tsx rendered it directly as a React child, crashing with
'Objects are not valid as a React child'.

- Update CronJob interface in api.ts to match actual API response
- Use schedule_display (string) instead of schedule (object)
- Use state instead of status for job state
- Use last_error instead of error for error display

web/src/lib/api.ts

@@ -222,12 +222,14 @@ export interface CronJob {
   id: string;
   name?: string;
   prompt: string;
-  schedule: string;
-  status: "enabled" | "paused" | "error";
+  schedule: { kind: string; expr: string; display: string };
+  schedule_display: string;
+  enabled: boolean;
+  state: string;
   deliver?: string;
   last_run_at?: string | null;
   next_run_at?: string | null;
-  error?: string | null;
+  last_error?: string | null;
 }
 
 export interface SkillInfo {