Withhold a site name that could be the recipe link's host

A page that names no site is stored under its host, which may be the
pasted link's (a token in a subdomain) or a redirect's. The dinner
detail now returns source.site_name only when the stored name could not
be a host: the link's own host, an IP address or a dotted host name is
withheld as null, so "Recipe from {site}" shows only real attribution.
The extractor's host fallback is shared as recipes.HostSiteName.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/dinners/dinners_test.go

@@ -1,6 +1,7 @@
 package dinners_test
 
 import (
+	"database/sql"
 	"encoding/json"
 	"errors"
 	"strings"
@@ -74,3 +75,46 @@ func TestCreateRegularNeverNamesFromLink(t *testing.T) {
 	}
 	check("duplicate error", dup.Error())
 }
+
+// TestPageSiteNameWithholdsHosts: a stored site name that could be a host —
+// the link's own, in any case and without "www.", an IP address or a dotted
+// host name — is withheld; a name the page gave, dotless or with spaces, is
+// kept.
+func TestPageSiteNameWithholdsHosts(t *testing.T) {
+	t.Parallel()
+	const link = "https://www.TokenHost/recipes/stew"
+	for _, tc := range []struct {
+		stored string
+		valid  bool
+		want   *string
+	}{
+		{"", false, nil},
+		{"tokenhost", true, nil},
+		{"TOKENHOST", true, nil},
+		{"private-token.example.com", true, nil},
+		{"Food.com", true, nil},
+		{"203.0.113.7", true, nil},
+		{"2001:db8::1", true, nil},
+		{"Delish", true, ptr("Delish")},
+		{"Bon Appétit", true, ptr("Bon Appétit")},
+		{"Mr. Food Test Kitchen", true, ptr("Mr. Food Test Kitchen")},
+	} {
+		got, err := dinners.PageSiteName(sql.NullString{String: tc.stored, Valid: tc.valid}, link)
+		if err != nil {
+			t.Fatalf("PageSiteName(%q): %v", tc.stored, err)
+		}
+		if (got == nil) != (tc.want == nil) || (got != nil && *got != *tc.want) {
+			t.Errorf("PageSiteName(%q) = %v, want %v", tc.stored, deref(got), deref(tc.want))
+		}
+	}
+	if _, err := dinners.PageSiteName(sql.NullString{String: "Delish", Valid: true}, "https://secret-token\x7f.example/%zz"); err == nil || strings.Contains(err.Error(), "secret-token") {
+		t.Errorf("PageSiteName of an unparseable link: err = %v, want one not quoting the link", err)
+	}
+}
+
+func deref(s *string) any {
+	if s == nil {
+		return nil
+	}
+	return *s
+}