refactor: Move files into src directory

Refactored project structure: Moved all Python modules to a src/ directory, updated imports accordingly. Added new environment variables to Dockerfile and docker-compose.yml. Removed Dockerfile.test and TODO file.

Dockerfile

@@ -5,6 +5,8 @@ FROM python:3.11-slim
 WORKDIR /app
 
 # Set environment variables using the ARG values
+ENV TARGET_RESERVATION_TIME=${TARGET_RESERVATION_TIME}
+ENV BOOKING_WINDOW_END_DELTA_MINUTES=${BOOKING_WINDOW_END_DELTA_MINUTES}
 ENV CROSSFIT_USERNAME=${CROSSFIT_USERNAME}
 ENV CROSSFIT_PASSWORD=${CROSSFIT_PASSWORD}
 ENV EMAIL_FROM=${EMAIL_FROM}