OxelLabs/IMS-SMS — reverse-engineered prompt

Build me a small Python web app called IMS SMS that can send text messages from a simple admin screen.

I want to enter a phone number and message, send it, see if it worked, and view a simple history of messages. Keep it easy to run locally and deploy on Railway, since the repo already has Railway and Procfile setup. Use environment variables for any SMS provider credentials and add a safe demo mode if keys are missing so I can test without sending real texts.

Add basic validation for phone numbers and blank messages, clear success and error messages, and a clean README with setup steps. Please use whatever lightweight Python web framework fits this repo and update main.py, requirements, and deployment files as needed. Look up current docs online if you need to.