A feed with no artwork takes its site's icon (#70)

When a feed names no image and none is stored, the scan fetches the
channel's site link (RSS <link>, Atom rel=alternate) and uses the
apple-touch-icon or icon it names, falling back to /favicon.ico when that
answers with an image.

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

src/main.rs

@@ -1205,7 +1205,15 @@ async fn scan_one(
         return sync_opml(ctx, id, feed_cfg, &bytes).await;
     }
 
-    let parsed = feed::parse(&bytes)?;
+    let mut parsed = feed::parse(&bytes)?;
+    // ponytail: a site with no icon at all is asked again on every scan that finds the feed
+    // changed; remember the miss in the feeds table if that turns out to cost.
+    if parsed.image.is_none()
+        && let Some(site) = &parsed.site
+        && ctx.db.feed_summary(id).await?.image.is_none()
+    {
+        parsed.image = feed::site_icon(&ctx.client, site).await;
+    }
     ctx.db.record_feed(
         id,
         &feed_cfg.url,