Error messages in sendMessageWhatsApp, sendReactionWhatsApp, and
sendPollWhatsApp included hardcoded \"WhatsApp\" references. This caused
confusion when cron jobs using other providers (e.g., Telegram) failed
with errors mentioning WhatsApp.
Changes error messages to be provider-agnostic while maintaining the
same error handling behavior.
Fixes#461Fixes#470
Co-Authored-By: Claude <noreply@anthropic.com>