feat: add model filter system with site-level batch disable, global brand filter, route status filter, and channel site-block shortcut

- Route status filter: add enabled/disabled filter chips to RouteFilterBar
- Channel site-block: add "站点屏蔽" button on channel rows to quickly
  add a model to a site's disabled list and trigger rebuild
- Site batch selection: new GET /api/sites/:id/available-models endpoint;
  Sites.tsx now shows a brand-grouped checkbox list for batch model disable
- Global brand filter: new brandMatcher.ts service; settings API and UI
  for blocking entire brands from route generation
- Fix infinite scroll race condition when sentinel ref is null during
  IntersectionObserver effect setup after filter changes

src/web/pages/sites.edit-scroll.test.tsx

@@ -8,6 +8,7 @@ const { apiMock } = vi.hoisted(() => ({
   apiMock: {
     getSites: vi.fn(),
     getSiteDisabledModels: vi.fn().mockResolvedValue({ models: [] }),
+    getSiteAvailableModels: vi.fn().mockResolvedValue({ models: [] }),
   },
 }));