Allow qBittorrent to be configured without credentials (supports IP whitelist) and require an API key for SABnzbd. Skip connection testing when disabling a client. Updates include: validation changes in admin and setup API routes, test-download-client flows, DownloadClientModal UI validation and save/test logic, and DownloadClientManager to pass empty strings for optional credentials. Tests updated to reflect SABnzbd API key requirement.
Implements support for configuring both qBittorrent and SABnzbd simultaneously, including migration from legacy config, protocol-aware routing, and protocol filtering. Adds new CRUD API routes for download clients, new UI management components, and updates setup and settings flows to use the new multi-client architecture. Updates documentation to describe the new structure and usage.
kikootwo