chore: Use /bin/dash explicitly in Dockerfile ENTRYPOINT

For consistency with the `entrypoint.sh` script's shebang (`#!/usr/bin/env dash`), this change updates the Dockerfile's ENTRYPOINT to call `/bin/dash` directly instead of `/bin/sh`.

This makes the choice of shell explicit and ensures the script is always executed by the intended interpreter, regardless of what `/bin/sh` might point to in future base images.

Dockerfile

@@ -76,5 +76,5 @@ RUN mkdir $SRTM_CACHE
 
 EXPOSE 4000
 
-ENTRYPOINT ["tini", "--", "/bin/sh", "/entrypoint.sh"]
+ENTRYPOINT ["tini", "--", "/bin/dash", "/entrypoint.sh"]
 CMD ["bin/teslamate", "start"]