library: add Quick Add page (scan an ISBN, the book is added)

A small standard-library Python service next to Koha:
- looks the code up via Z39.50 (yaz) then Open Library over HTTPS
- checks Koha for an existing copy (ISBN-10/13 and UPC/EAN aware)
- adds the record + an item with the next barcode via Koha's REST API
- scanner-friendly UI: auto-focus, audible feedback, duplicate card with
  'add another copy', manual entry when nothing is found, undo, and the
  barcode range to print labels for
Also: enable RESTBasicAuth, map 024$a to the ean column, wire the service,
port and credentials into compose/install.sh.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013wi3ZSot4XbUViwRFgLpRf

library/quickadd/Dockerfile

@@ -0,0 +1,26 @@
+# Quick Add: scan an ISBN, the book is in the catalogue. Standard-library Python
+# plus yaz (the Z39.50 client). Same Debian base as the Koha image, so it adds
+# one small layer instead of another base-image pull.
+FROM debian:bookworm-slim
+ENV DEBIAN_FRONTEND=noninteractive PYTHONUNBUFFERED=1
+
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends ca-certificates python3 yaz tzdata \
+ && rm -rf /var/lib/apt/lists/*
+
+# Optional: drop extra CA certificates (*.crt) into ./certs/ before building if
+# you are behind a TLS-inspecting proxy. Empty by default.
+COPY certs/ /usr/local/share/ca-certificates/extra/
+RUN update-ca-certificates
+
+RUN useradd --system --uid 10001 --home-dir /app quickadd \
+ && mkdir -p /app /data && chown quickadd /data
+COPY app.py index.html /app/
+USER quickadd
+WORKDIR /app
+
+EXPOSE 8082
+VOLUME ["/data"]
+HEALTHCHECK --interval=30s --timeout=5s --retries=3 \
+  CMD python3 -c "import urllib.request,sys; sys.exit(0 if urllib.request.urlopen('http://127.0.0.1:8082/healthz', timeout=3).status==200 else 1)"
+CMD ["python3", "/app/app.py"]