Replace the WhatsappCall model with the unified Call model introduced
in feat/voice-call-model (PR #14026), enabling multi-provider support
(Twilio + WhatsApp) under a single data model.
Key changes:
- Delete WhatsappCall model and its 3 migrations (whatsapp_calls table)
- Enhance Call model with WhatsApp-specific helpers (sdp_offer,
ice_servers, recording_url, direction_label, ringing?, in_progress?)
- Update all backend services, controller, and jobs to use Call model
- Map statuses: accepted→in_progress, rejected→failed, missed→no_answer,
ended→completed
- Map directions: inbound→incoming, outbound→outgoing (enums)
- Rename call_id column to provider_call_id, always set provider: :whatsapp
- Add authorization check on initiate action
- Add race condition guard in outbound call_connect webhook handler
- Consolidate direction_label helper into Call model (DRY)
- Update frontend data key from waCallId to callId in VoiceCall bubble
- Remove whatsapp_calls table from schema.rb, fix missing started_at
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
