Demonstrates sending an SMS, verifying credentials, and checking balance.

1. Create a .env file with your credentials
2. Use KwtSMS.fromEnv() to load them automatically
3. Call verify() to test credentials
4. Call send() to send a message

• Always call verify() first to confirm credentials are valid
• Save msgId from the send response for status tracking and delivery reports
• Save balanceAfter from the send response to avoid extra API calls
• Use testMode=true during development (no credits consumed)