feat: internal links widget with counts and suggestions

- E10 golem15-seo-links in the SEO tab after the graph preview (types
  with a body): inbound and outbound counts from the last finished crawl,
  the orphan warning, up to 10 pages to link to (Copy address) and 10
  that could link here
- classes/linkgraph.go builds the report from the crawl's pages and
  links; the crawler's orphan suggestions share NormalText
- GET /_seo/api/v1/links and seo_get_link_suggestions; widget action
  seo_links mapped in AdminOperations
- element bundle rebuilt

lang/en/lang.yaml

@@ -20,6 +20,7 @@ permissions:
 tab:
     seo: SEO
 field:
+    links: Internal links
     snippet: Search result preview
     description_comment: Leave empty to use the description template, then the content's own excerpt.
     keyphrase: Focus keyphrase

lang/pl/lang.yaml

@@ -20,6 +20,7 @@ permissions:
 tab:
     seo: SEO
 field:
+    links: Linki wewnętrzne
     snippet: Podgląd w wynikach wyszukiwania
     description_comment: Zostaw puste, aby użyć szablonu opisu, a potem zajawki treści.
     keyphrase: Fraza kluczowa