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/.gitignore

@@ -2,3 +2,4 @@
 .env
 # Extra CA certificates dropped in for building behind a proxy
 koha/certs/*.crt
+quickadd/certs/*.crt