- docker/rootfs/usr/local/share/prosody-plugins/mod_user_api.lua: new POST /user-api/register endpoint (JSON, validation, reserved names, per-IP rate limit, refuses when AUTH_TYPE is not internal)
- docker/rootfs/usr/local/bin/entrypoint.sh: read ENABLE_REGISTRATION, load user_api on the main host only when ENABLE_AUTH is on, warn otherwise
- docker/compose.yml: add ENABLE_REGISTRATION
- README.md: document registration
- docker/rootfs/usr/local/share/prosody-plugins/mod_auth_openfire_hybrid.lua: moved from docker/rootfs/prosody-plugins-contrib/ (rootfs top level may only hold root/, tmp/, usr/)
- docker/rootfs/usr/local/bin/entrypoint.sh: add /usr/local/share/prosody-plugins to plugin_paths