fix: Fix matplotlib cache and import entrypoint

Author: Linked-Liszt

docker/downloader.Dockerfile

@@ -10,7 +10,8 @@ WORKDIR /app
 COPY src/downloader/requirements.txt /tmp/requirements.txt
 RUN pip install --no-cache-dir -r /tmp/requirements.txt
 
-ENV MPLCONFIGDIR=/app/.cache/matplotlib
+ENV XDG_CACHE_HOME=/tmp/.cache
+ENV MPLCONFIGDIR=/tmp/.cache/matplotlib
 
 # Code and configs are mounted at runtime via docker-compose volumes:
 #   - ./src/downloader -> /app

src/simulator/__init__.py

@@ -1 +1 @@
-from .diffraction_generator import DiffractionGenerator
+__all__ = ["diffraction_generator", "simulation_worker"]