[Broadcast] Scheduling system

[viganogabriele]

Parent Epic: #120

Part of #120

Implement the scheduling system for delayed message delivery.

Requirements

• Store scheduled announcements in database with:
  • Message content (including media file_id)
  • Target tag number
  • Status (pending, sent, cancelled)
  • Scheduled datetime
  • Creation datetime
  • Creator admin ID
• Implement a cron job / scheduler that:
  • Checks for pending announcements
  • Triggers delivery when scheduled time is reached
  • Handles bot restart without losing scheduled jobs
• Support:
  • Immediate delivery (trigger right away)
  • Scheduled delivery (at specific datetime)
  • Cancel pending announcements

Technical Notes

• Consider using a job queue (Bull, Agenda, etc.) or built-in scheduling
• Handle timezone correctly
• Ensure atomic status updates

Labels: enhancement