Reassign a booked call to a different closer

Swap the host on a booked upcoming call. Under the hood this cancels the existing calendar event and creates a fresh one under the new closer's calendar, then fires the call.closer_reassigned webhook.

Constraints:

• Call must be in booking kind (intent calls cannot be reassigned)
• Call must be in the future (past calls need the outcome flow instead)
• Call must not already be cancelled
• New closer must already have a connected calendar grant
• Cross-org reassignment is blocked

Side effects visible to Partner API consumers:

• DB row's closer_id / closer_email / closer_name / nylas_event_id / nylas_grant_id / conferencing_link are updated atomically
• New conferencing link is issued (old one is invalidated)
• call.closer_reassigned webhook fires to all subscribers

NOT done via the Partner API (to keep this a pure data operation):

• No customer email is sent — the Partner is expected to handle outbound communication using the data in the webhook payload
• No Zapier/internal event is emitted — the call.closer_reassigned webhook IS the Partner API's event bus

curl -X POST "https://api.aura-app.ai/v1/calls/550e8400-e29b-41d4-a716-446655440000/reassign-closer" \  -H "Content-Type: application/json" \  -d '{    "new_closer_id": "user_2abc123xyz"  }'

{
  "data": {
    "call_id": "call_abc_123",
    "conferencing_link": "string",
    "new_closer_id": "string",
    "new_closer_name": "string",
    "new_event_id": "string",
    "old_event_orphaned": false,
    "previous_closer_id": "string",
    "previous_closer_name": "string"
  },
  "success": true
}

{
  "code": "NOT_FOUND",
  "error": "Lead not found",
  "requestId": "req_abc123",
  "success": false
}

{
  "code": "NOT_FOUND",
  "error": "Lead not found",
  "requestId": "req_abc123",
  "success": false
}

{
  "code": "NOT_FOUND",
  "error": "Lead not found",
  "requestId": "req_abc123",
  "success": false
}

{
  "code": "NOT_FOUND",
  "error": "Lead not found",
  "requestId": "req_abc123",
  "success": false
}