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.
Introduced a Vitest-based backend unit testing framework with supporting scripts, helpers, and GitHub Actions integration. Refactored the admin settings page to a modular architecture, splitting monolithic logic into feature-specific tabs and hooks for improved maintainability and testability. Updated documentation to reflect the new testing setup and settings architecture, and added new dependencies for testing utilities.