feat: JSON-LD graph, breadcrumbs and hreflang in the resolve answer (tracer)

- classes/schema builds one @graph per page (WebPage, article, profile,
  service, BreadcrumbList, VideoObject, WebSite, publisher) linked by @id
- breadcrumb trail through the primary parent chain, hreflang alternates
  with x-default, html_lang and og:locale in the resolve answer
- migration 202610280004 adds the publisher, local business, home crumb
  and pagination settings columns

config/config.yaml

@@ -32,3 +32,15 @@ notfound_max_rows: 10000
 # POST /_seo/api/v1/registry/routes (the page registry). Empty uses
 # notfound_token; both empty turn the report off (it answers 404).
 route_report_token: ""
+#
+# og_locales maps locale codes to their og:locale values (the resolve
+# answer's seo.og.locale and locale_alternates). Codes not listed use
+# pl_PL, en_US and de_DE for pl, en and de, else the language with its
+# region (pt-BR: pt_BR) or the language doubled (fr: fr_FR):
+# og_locales: {pl: pl_PL, en: en_GB}
+#
+# search_url is the site search address with the {search_term_string}
+# placeholder, for example /szukaj?q={search_term_string}. When set, the
+# WebSite node of the JSON-LD graph carries a SearchAction. Empty means no
+# SearchAction:
+# search_url: "/szukaj?q={search_term_string}"