feat: add status dashboard for live agent monitoring

Dedicated Discord channel shows per-group agent status with live
elapsed time. Single message is edited every 10s instead of spamming.

- GroupQueue tracks startedAt timestamps and exposes getStatuses()
- Channel interface gets editMessage/sendAndTrack for message editing
- STATUS_CHANNEL_ID env var to configure the dashboard channel
- Shows processing/idle/waiting/inactive per registered group

src/config.ts

@@ -56,6 +56,10 @@ export const TRIGGER_PATTERN = new RegExp(
   'i',
 );
 
+// Status dashboard: Discord channel ID for live agent status updates
+export const STATUS_CHANNEL_ID = process.env.STATUS_CHANNEL_ID || '';
+export const STATUS_UPDATE_INTERVAL = 10000; // 10s
+
 // Timezone for scheduled tasks (cron expressions, etc.)
 // Uses system timezone by default
 export const TIMEZONE =