Just http://<pi-ip> now instead of http://<pi-ip>:8080. Safe since
the systemd service already runs as root (needed for GPIO/SPI access
anyway), so binding the privileged port isn't a new requirement.
Local --mock dev stays on 8080 (README/main.py default unchanged) --
that's normally run without root, and port 80 needs it.
install.sh now does enable + restart instead of enable --now, so
re-running it after a unit-file change (like this one) actually
applies on an already-installed instance, not just a fresh install.