Enhance: Twitch multi-streamer support and fix timer listall

- Twitch add: multiple streamers via comma separation
- Twitch add: optional discord channel (defaults to current)
- Twitch remove: multiple streamers via comma separation
- Twitch listall: new command showing all server streamers (admin)
- Timer listall: fix SQL error by removing invalid JOIN

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/commands/utility/timer.ts

@@ -293,7 +293,7 @@ const command: Command = {
             }
 
             const reminders: any[] = DB.all(
-                'SELECT r.*, c.name as channel_name FROM reminders r LEFT JOIN channels c ON r.channel_id = c.id WHERE r.guild_id = ? ORDER BY r.target_time ASC',
+                'SELECT * FROM reminders WHERE guild_id = ? ORDER BY target_time ASC',
                 guildId
             );