Drop legacy AIOS tables (aios_inbox, aios_outbox, aios_heartbeat)

Context

The AIOS v1 architecture used three tables for external message handling:

• aios_inbox — inbound messages from Telegram via Docker bridge
• aios_outbox — outbound responses
• aios_heartbeat — loop lifecycle tracking

As of the v2 migration (2026-03-24), these are effectively legacy:

• CC channels handle Telegram natively (no Docker bridge needed)
• The Docker bridge is retired (docker update --restart=no)
• Only 8 messages ever went through the inbox (5 processed)
• Sprint orchestration's agent_inbox replaces internal dispatch

Action

Once CC channels + sprint system has been stable for 2+ weeks:

1. Verify no active references to aios_inbox, aios_outbox, aios_heartbeat
2. Back up the 8 inbox rows + 3 outbox rows (if any) for historical record
3. Create migration to drop all 3 tables
4. Remove any remaining references in server code or skills

Not urgent — safety window

The custom bridge source is kept at bridges/telegram/ for a 2-week rollback window (expires ~2026-04-07). Do not drop tables before that date.