Replaces the override rule system with a new priority-based routing rules engine. Routing rules are
evaluated top-to-bottom with first-match-wins semantics, supporting conditions on users, genres,
languages, and keywords. Quality profiles, root folders, minimum availability, series type, and tags
move from instance-level settings to routing rules with support for instance switching, with
fallback rules acting as catch-all defaults. Includes a migration to convert existing instance
defaults and override rules into the new system, a routing resolver used at request time, updated
OpenAPI spec, and a new UI with drag-and-drop reordering, filter tabs, and inline rule expansion.
fix#232, fix#1560, fix#2058
