- Add mci_send_record table and entity/mapper
- Add SendService with target resolution (conversation/person/person_list/tag/rule)
- Add /api/v1/send, /api/v1/send/test, /api/v1/send/{task_id}/records
- Add test send simulation without channel dispatch
- Dispatch real sends through ChannelAdapterRegistry (placeholder until Phase 6)
- Add SendControllerTest and fix missing deleted column on account-conversation binding