fix: use python entrypoint in Dockerfile

Avoid shell expansion issues with PORT in Railway by running main.py.

Author: kodjima33

Dockerfile

@@ -20,5 +20,5 @@ COPY . .
 # Expose port (Railway will set $PORT)
 EXPOSE 8000
 
-# Run the application
-CMD uvicorn main:app --host 0.0.0.0 --port ${PORT:-8000}
+# Run the application (Railway provides PORT)
+CMD ["python", "main.py"]