Register a new user and organization

curl -X POST 'https://api.expiryedge.com/v1/register' \
  -H "Content-Type: application/json" \
  -d '{
  "email": "priya.shah@northwinddental.com",
  "password": "Str0ng!Passw0rd",
  "firstName": "Priya",
  "lastName": "Shah",
  "displayName": "Priya Shah",
  "is_organization": true,
  "organization_name": "Northwind Dental",
  "timezone": "America/Chicago",
  "recaptchaToken": "03AFcWeA6x..."
}'

{
  "message": "User registered successfully",
  "user": {
    "id": "u_71bXq",
    "email": "priya.shah@northwinddental.com",
    "firstName": "Priya",
    "lastName": "Shah",
    "displayName": "Priya Shah",
    "user_type": "organization",
    "organization_id": "org_northwind"
  }
}