Issue #3569589: Add international SMS support (smsapi.com, smsapi.se, smsapi.bg)
- Add smsapi_service_region config option (PL, COM, SE, BG)
- Add region selector dropdown in configuration form
- Add getService() helper method to return correct service based on region
- Replace all hardcoded smsapiPlService() calls with getService()
- Default to 'PL' for backward compatibility
Closes #3569589