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/config/env_internal_test.go

@@ -65,7 +65,7 @@ func TestEnvironmentSetsEveryKey(t *testing.T) {
 	t.Setenv("PIXA_METRICS_PASSWORD", "metricspass")
 	t.Setenv("PIXA_SIGNING_KEY", validTestSigningKey)
 	t.Setenv("PIXA_ALLOWLIST_HOSTS", "s3.sneak.cloud,.example.com")
-	t.Setenv("PIXA_REFERER_BLOCKLIST", "leech.example,.hotlinker.example")
+	t.Setenv("PIXA_REFERER_BLOCKLIST", "hotlinker.example,.leech.example")
 	t.Setenv("PIXA_ALLOW_HTTP", "true")
 	t.Setenv("PIXA_UPSTREAM_CONNECTIONS_PER_HOST", "5")
 	t.Setenv("PIXA_UPSTREAM_CONNECTIONS", "10")
@@ -94,7 +94,7 @@ func TestEnvironmentSetsEveryKey(t *testing.T) {
 		MetricsPassword:            "metricspass",
 		SigningKey:                 validTestSigningKey,
 		AllowlistHosts:             []string{testHostS3, ".example.com"},
-		RefererBlocklist:           []string{"leech.example", ".hotlinker.example"},
+		RefererBlocklist:           []string{"hotlinker.example", ".leech.example"},
 		AllowHTTP:                  true,
 		UpstreamConnectionsPerHost: 5,
 		UpstreamConnections:        10,