Add read-only mode support and enhance logging throughout the application

Dockerfile

@@ -9,6 +9,7 @@ FROM scratch
 
 # Group ID 20 is dialout, needed for tty read/write access
 USER 3000:20
+ENV READ_ONLY=false
 COPY --from=builder /build/invertergui /bin/
 ENTRYPOINT [ "/bin/invertergui" ]
 EXPOSE 8080