feat(sources): site kinds and capabilities (IA-2)

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]>

packages/contracts/src/capabilities-io.ts

@@ -25,8 +25,10 @@ import {
   SiteAccountUserData,
   SiteAdapter,
   SiteAuthKind,
+  SiteCapability,
   SiteHealth,
   SiteHealthResult,
+  SiteKind,
   SiteLastHealth,
   SiteLoginResult,
   SiteUserDataPoint,
@@ -430,6 +432,10 @@ export const SiteBrief = z.object({
   id: Id,
   key: z.string(),
   name: z.string(),
+  /** 站点类型:pt / public_bt / rss_feed / torznab */
+  kind: SiteKind,
+  /** 实际可用的获取方式(search / list / rss / detail / login / userinfo) */
+  capabilities: z.array(SiteCapability),
   adapter: SiteAdapter,
   baseUrl: z.string(),
   enabled: z.boolean(),