Releases on Gitea, one-line installer and auto-update (1.1.0)

- .github/workflows/release.yml: a tag vX.Y.Z runs the tests, publishes
  daynivo-kiosk-os-X.Y.Z.tar.gz (+ .sha256) and install-online.sh as a
  Gitea release, then builds the SD image with pi-gen and attaches it.
- install-online.sh: curl | sudo bash installer for the latest release.
- voxip-kiosk-updater: checks the latest release, verifies and unpacks a
  newer one under /opt/daynivo-kiosk-os and runs its update.sh. A daily
  timer checks around 03:00 and installs when auto_update is on.
- Web interface: Systeem -> Software-updates with the auto-update switch,
  check now and install now (helper verbs update-check / update-install).
- CI checks out with plain git, so it runs on Gitea's act_runner too.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Makefile

@@ -22,7 +22,7 @@ test-bookworm:
 		apt-get update -qq && DEBIAN_FRONTEND=noninteractive apt-get install -y -qq --no-install-recommends \
 		python3 python3-flask python3-argon2 python3-websocket python3-pytest shellcheck >/dev/null && \
 		cp -r /src /work && cd /work && rm -rf .venv && python3 -m pytest -p no:cacheprovider && \
-		shellcheck -S warning install.sh update.sh uninstall.sh image/build.sh bin/voxip-kiosk-x'
+		shellcheck -S warning install.sh install-online.sh update.sh uninstall.sh tools/release-upload.sh image/build.sh bin/voxip-kiosk-x'
 
 # Web interface on http://127.0.0.1:8080 with throwaway state in .dev/ (system actions fail gracefully).
 dev: