build: enforce portable line endings

docker/core.Dockerfile

@@ -70,8 +70,10 @@ ENV PATH="/opt/venv/bin:/usr/local/bin:$PATH" \
     PI_BIN=pi \
     HOME=/home/thoth
 
+COPY scripts/verify-line-endings.sh /usr/local/bin/verify-line-endings
 COPY docker/core-entrypoint.sh docker/session-migrate.sh docker/ensure-pi-trust.mjs /app/docker/
-RUN chmod +x /app/docker/core-entrypoint.sh /app/docker/session-migrate.sh
+RUN /usr/local/bin/verify-line-endings /app/docker \
+ && chmod +x /app/docker/core-entrypoint.sh /app/docker/session-migrate.sh
 
 WORKDIR /app/backend
 USER thoth