site.kind: pt / public_bt / rss_feed / torznab. Each kind declares the
acquisition modes it may support (search, list, rss, detail, login,
userinfo); a site's effective capabilities = kind ∩ site definition.
torznab only defines TorznabSiteConfig and cannot be added yet.
Migration 0055: generic_rss sites become rss_feed, the rest pt; feeds
without a site are grouped by host into new custom RSS source sites
(cursor window and conditional headers cleared so the next fetch writes
releases). User DB read-only dry-run: 0 orphan feeds.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
