The directory's refresher refuses internal addresses (#329)

The refresher fetches every feed a snapshot names, and anyone with a
write token sends snapshots; a listed feed's redirect goes wherever its
publisher likes. Nothing checked the destination, so the directory
fetched loopback, its Docker network and the LAN, and what answered
became a listing's title and description on its public pages.

Its client now has ipx-feed's guard (#320) with nothing allowed: no
feed the directory lists is on this network.

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

crates/directory/src/lib.rs

@@ -144,6 +144,9 @@ impl Directory {
             .read_timeout(ipx_feed::FEED_SILENCE)
             .redirect(reqwest::redirect::Policy::none())
             .user_agent(concat!("ipx-directory/", env!("CARGO_PKG_VERSION")))
+            // The feeds are named by whoever holds a write token, and redirect where their
+            // publishers like; none is on this network, so nothing here is fetched (#329).
+            .connector_layer(ipx_feed::guard::Guard::new(Default::default()))
             .build()?;
         Ok(Arc::new(Self {
             store,
@@ -568,6 +571,16 @@ mod tests {
         assert_eq!(got["accepted"], 1);
     }
 
+    #[tokio::test]
+    async fn the_refresher_fetches_nothing_on_this_network() {
+        let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+        tokio::spawn(async move { while listener.accept().await.is_ok() {} });
+        let (_, dir) = app().await;
+        let err = dir.client.get(format!("http://{addr}/feed.xml")).send().await.unwrap_err();
+        assert!(format!("{err:?}").contains("internal address"), "{err:?}");
+    }
+
     #[tokio::test]
     async fn the_public_pages_read_the_list_once_a_minute() {
         let (_, dir) = app().await;