feat: pagination forms and suffixes in resolve and site

- Pagination tab: query or path form, per-locale segment, title and
  description suffixes with %page% and %pages%
- ?page=1, /<segment>/1 and the other form answer 301 to the configured
  address in one hop with normalisation and strict URLs; a page value
  that is not a number answers not_found with pagination.invalid
- page 2 and later: self canonical with the page, index,follow, the
  suffixes (%pages% left for the layer), paged hreflang alternates
- GET /site answers pagination {form, param, segments} and home_crumb

settings_test.go

@@ -31,7 +31,7 @@ func TestSettingsTypeTabs(t *testing.T) {
 		env := bootEnv(t)
 		token := env.admin(t, true)
 		fields := env.formSchema(t, token, "golem15/seo/settings")
-		if got, want := strings.Join(tabsOf(fields), " | "), "General | Page | Tags | Notes | Site page | Indexing | Addresses | Links | Publisher | Local business | Verification"; got != want {
+		if got, want := strings.Join(tabsOf(fields), " | "), "General | Page | Tags | Notes | Site page | Indexing | Addresses | Pagination | Links | Publisher | Local business | Verification"; got != want {
 			t.Fatalf("settings tabs = %q, want %q", got, want)
 		}
 		findField(t, fields, "type_acme_page_inject")
@@ -81,7 +81,7 @@ func TestSettingsTypeTabs(t *testing.T) {
 	t.Run("no other content types", func(t *testing.T) {
 		env := bootPlugins(t, []string{"golem15.seo"})
 		token := env.admin(t, true)
-		if got, want := strings.Join(tabsOf(env.formSchema(t, token, "golem15/seo/settings")), " | "), "General | Site page | Indexing | Addresses | Links | Publisher | Local business | Verification"; got != want {
+		if got, want := strings.Join(tabsOf(env.formSchema(t, token, "golem15/seo/settings")), " | "), "General | Site page | Indexing | Addresses | Pagination | Links | Publisher | Local business | Verification"; got != want {
 			t.Fatalf("settings tabs = %q, want %q", got, want)
 		}
 	})