Audiobooks: talk to OpenAudible directly with its own username and password (OPENAUDIBLE_URL)

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

docker-compose.yml

@@ -23,6 +23,7 @@ services:
       MS_CLIENT_SECRET: ${MS_CLIENT_SECRET:-}
       LYRICS_API_URL: http://127.0.0.1:9999                  # the bundled lyrics service (Lyrica, below, shares this container's network); remove this line and the service to skip it
       SIGNAL_API_URL: http://127.0.0.1:8085                  # the bundled Signal bridge (below, shares this container's network); remove this line and the service to skip Signal
+      OPENAUDIBLE_URL: ${OPENAUDIBLE_URL:-}                # audiobooks straight from OpenAudible (e.g. http://172.16.16.106:8000); the username and password in Settings -> Audiobooks sign-in are OpenAudible's. Leave empty to go through the audiobook player instead
       PODCAST_URL: ${PODCAST_URL:-https://podcast.necloud.us/}
       PODGRAB_PASSWORD: ${PODGRAB_PASSWORD:-}                # Podgrab's PASSWORD setting, if it has one (the sign-in name is always podgrab); stays on the server
       ONLYOFFICE_JWT_SECRET: ${ONLYOFFICE_JWT_SECRET:-}    # same value as the OnlyOffice server's JWT secret