feat: auto-link phrases in the resolve answer (tracer)

- golem15_seo_autolinks (migration 202610280007) and the settings column
  autolink_max (Links tab, 0 to 20, default 3)
- classes/autolinks.go: checked save and delete with history, ForPage
- ok resolve answers carry autolinks for the page's locale without
  disabled phrases and links to the page itself, and autolink_max

classes/history.go

@@ -295,10 +295,11 @@ var (
 	purging map[gorm.ConnPool]bool
 )
 
-// purgeSlug is the purge's slug: "*" for the settings and robots.txt,
-// else the changed object's address.
+// purgeSlug is the purge's slug: "*" for the settings, robots.txt and an
+// auto-link phrase (it may appear in any text), else the changed object's
+// address.
 func purgeSlug(c Change) string {
-	if c.Kind == models.SubjectSettings || c.Kind == models.SubjectRobots {
+	if c.Kind == models.SubjectSettings || c.Kind == models.SubjectRobots || c.Kind == models.SubjectAutolink {
 		return "*"
 	}
 	for _, values := range []map[string]any{c.After, c.Before} {