feat: Follow-up Tracker for Unanswered Messages

[gromdimon]

Summary

Track messages that haven't received replies and enable auto-chase functionality.

Features

• List messages waiting for reply with elapsed time
• Warning indicator when waiting too long (24h default)
• Quick actions: Chase now, Snooze, Mark done
• Auto-chase option per contact

Proposed UI

┌─────────────────────────────────────────┐
│  Waiting for Reply                      │
├─────────────────────────────────────────┤
│  Mike - Invoice question      24h ago ⚠️│
│  [Chase now] [Snooze 24h] [Mark done]   │
│                                         │
│  Sarah - Meeting confirm       2h ago   │
│  [Chase now] [Snooze 24h] [Mark done]   │
└─────────────────────────────────────────┘

Technical Considerations

• Store sent message timestamps in task ledger
• Track reply status per conversation
• Configurable chase threshold per contact

Acceptance Criteria

• Track outgoing messages waiting for reply
• Time-based alerts
• Manual chase action
• Auto-chase toggle per contact
• Snooze functionality