fix: macOS bcopy conflict and Docker host binding

- Fix #11: Guard bcopy/bzero declarations with _VISUALCPP in commoninclude.h
  to avoid redefinition errors on macOS where <strings.h> provides them
- Fix #12: Add --host flag to serve command, default 127.0.0.1
  Docker now binds to 0.0.0.0 so Colima can reach the server from host
- Also fix truncate() panic when n < 3

Dockerfile

@@ -34,4 +34,4 @@ COPY scripts/extract_wavs.sh /usr/local/bin/
 WORKDIR /data
 EXPOSE 8080
 ENTRYPOINT ["fetch"]
-CMD ["serve", "-p", "8080"]
+CMD ["serve", "-p", "8080", "--host", "0.0.0.0"]