feat: links settings and outbound rules in resolve

- migration 202610280003: settings links_new_tab (default on),
  nofollow_domains and sponsored_domains; robots llms_enabled and
  llms_intro (used by the llms.txt commit)
- SEO settings Links tab: the new-tab switch and the two domain lists,
  one domain per line, lowercased, refused with settings.domain_invalid
  naming the line; writable through seo_update_settings
- the resolve answer of an ok page carries outbound {new_tab,
  nofollow_domains, sponsored_domains}; no existing key changes

models/settings/fields.yaml

@@ -3,8 +3,8 @@
 # ===================================
 #
 # SEO settings (UI-SPEC C11): General, one tab per content type (added by
-# the plugin's form extension after General), Indexing, Addresses and
-# Verification.
+# the plugin's form extension after General), Indexing, Addresses, Links
+# (UI-SPEC C20) and Verification.
 
 fields:
     _staging:
@@ -139,6 +139,30 @@ fields:
         default: false
         tab: golem15.seo::lang.settings.tab_urls
 
+    links_new_tab:
+        label: golem15.seo::lang.settings.links_new_tab
+        comment: golem15.seo::lang.settings.links_new_tab_comment
+        type: switch
+        span: right
+        default: true
+        tab: golem15.seo::lang.settings.tab_links
+
+    nofollow_domains:
+        label: golem15.seo::lang.settings.nofollow_domains
+        comment: golem15.seo::lang.settings.domains_comment
+        type: textarea
+        size: small
+        span: left
+        tab: golem15.seo::lang.settings.tab_links
+
+    sponsored_domains:
+        label: golem15.seo::lang.settings.sponsored_domains
+        comment: golem15.seo::lang.settings.domains_comment
+        type: textarea
+        size: small
+        span: right
+        tab: golem15.seo::lang.settings.tab_links
+
     verify_google:
         label: golem15.seo::lang.settings.verify_google
         comment: golem15.seo::lang.settings.verify_code_comment