Read referer_blocklist through strictLoader and fix test lint

newFromSmartConfig went over the line limit, so referer_blocklist is now
read through strictLoader, like the other typed settings, instead of its
own parse step. The tests stop repeating string literals that goconst
counts: the environment test uses other hosts, two case names change, and
the handler test names each image route's URL instead of its path.

Model: opus-5-5

internal/handlers/referer_blocklist_internal_test.go

@@ -133,19 +133,24 @@ func TestRefererBlocklist(t *testing.T) {
 			"https://hotlinker.example.evil.example/", http.StatusOK},
 	}
 
-	for _, route := range []string{"/v1/image/", "/v1/e/"} {
+	// The photo's URL on each image route.
+	photoURLs := map[string]func(t *testing.T, h *Handlers) string{
+		"plain URL": func(t *testing.T, _ *Handlers) string {
+			t.Helper()
+
+			return photoURL(allowlistedHost)
+		},
+		"encrypted URL": encPhotoURL,
+	}
+
+	for urlName, photoURLFor := range photoURLs {
 		for _, tc := range cases {
-			t.Run(route+" "+tc.name, func(t *testing.T) {
+			t.Run(urlName+", "+tc.name, func(t *testing.T) {
 				t.Parallel()
 
 				routes, h, fetcher := newRefererRoutes(t)
 
-				target := photoURL(allowlistedHost)
-				if route == "/v1/e/" {
-					target = encPhotoURL(t, h)
-				}
-
-				rec := getWithReferer(t, routes, target, tc.referer)
+				rec := getWithReferer(t, routes, photoURLFor(t, h), tc.referer)
 
 				if tc.want == http.StatusOK {
 					requireServedPhoto(t, rec)