Add Library Catalog addon, lib/docker.sh and tests

- lib/docker.sh: shared Docker/Compose tooling (on-demand install via apt or
  get.docker.com, compose wrapper, container state/health, HTTP wait)
- menus/addon_library.sh: install/update/uninstall the Koha + Quick Add stack
  from library/ to /opt/kiosk-library, add the catalogue as a kiosk page
  (duration 0), choose kiosk-only vs LAN access, show addresses and login
- wire into install.sh menu, complete_uninstall and clone_settings
- tests/addon_library.test.sh: 41 checks against a stub sudo/docker and a
  fixture stack (no root, Docker or network needed)

Note: the 'network access' choice relies on a BIND_ADDR setting in the
library stack, added in a follow-up commit.

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

menus/clone_settings.sh

@@ -65,6 +65,7 @@ clone_detect_addons() {
     command -v netbird &>/dev/null && addons+=("netbird")
     baresip_is_installed 2>/dev/null && addons+=("asterisk_intercom")
     webui_is_installed 2>/dev/null && addons+=("webui")
+    library_is_installed 2>/dev/null && addons+=("library")
 
     if sudo -u "$KIOSK_USER" test -f "$CONFIG_PATH" 2>/dev/null; then
         local authelia_url
@@ -243,6 +244,13 @@ action_apply_clone_settings() {
                 fi ;;
             asterisk_intercom)
                 echo "  [!] Asterisk Intercom - needs its own SIP extension on this device" ;;
+            library)
+                if library_is_installed; then
+                    echo "  [x] Library Catalog - already installed (the books themselves are not cloned)"
+                else
+                    echo "  [ ] Library Catalog - not installed, install via Addons (the catalogue page is cloned, the books are not)"
+                    missing_any=true
+                fi ;;
             authelia)
                 echo "  [!] Authelia - needs a fresh login on this device" ;;
             *)