Detect stale gigs and send Discord reminders when status has not been updated

[michaelmwu]

Problem

We often lose track of a gig after it has been posted. Even if we add pending-gig tracking and manual status commands, the workflow will still drift unless the bot actively nudges us when a gig looks stale.

Scope

Add reminder / stale-detection automation for pending gigs so the bot can surface gigs that likely need a status check or cleanup.

Suggested Behavior

• Periodically scan pending gigs in local storage
• Detect gigs that have not had a status update or activity change within a configurable threshold
• Send a reminder in Discord when a gig appears stale
• Include enough context in the reminder to make the next action obvious
• Allow staff to update the status directly after the reminder

Examples of stale conditions:

• still marked recruiting after N days with no updates
• no applicant changes for N days
• original gig post still visible but local status is still unknown
• gig is effectively inactive and should probably be marked filled or outdated

Reminder UX

Suggested reminder content:

• link to the original gig post
• current internal status
• current visible Discord tag
• age since last status change
• applicant count
• suggested actions such as mark recruiting / filled / outdated / unknown

This can be implemented either as:

• a message in an internal staff channel
• a thread reply / follow-up near the original gig post
• a scheduled digest message

Exact UX can be decided during implementation.

Implementation Notes

• Reuse the existing worker/scheduler pattern for periodic jobs
• Store last_status_changed_at and/or last_activity_at on the local engagement record
• Keep reminders idempotent enough to avoid spam
• Consider reminder suppression / snooze behavior for recently acknowledged gigs

Acceptance Criteria

• The system can identify pending gigs that appear stale based on configurable rules
• The bot can send a Discord reminder for stale gigs
• Reminders include a link back to the original gig and enough state to decide what to do next
• The reminder flow does not spam repeatedly for the same unchanged gig
• Reminder thresholds are configurable

Parent

Part of #249
Related to #252