Favicon, level file icons, and a feed error mark in the triangle's column

- The logo as favicon, squared up (it is 128x121), at /favicon.png and at
  /favicon.ico outside the auth layer, where a browser asking on its own got a
  401; an apple-touch-icon on white (#32).
- An item not yet downloaded had its download bar on a line of its own under the
  file icon, lifting the icon above its row's; the bar now sits under it without
  taking space (#31).
- A feed error is Font Awesome's exclamation, hung in the margin where a folder's
  triangle is, in the same column; a folder holding a failing feed has its
  triangle turn red.

Closes #31, #32.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/feeds.ts

@@ -83,13 +83,15 @@ function renderFeeds(){
     el.tabIndex=0; el.dataset.id=f.id;
     const open = !!(kids && (expanded.has(f.id) || q));
     el.innerHTML =
-      (kids?`<button class="chev" aria-expanded="${open}" title="Show or hide the feeds inside" aria-label="Show or hide the feeds inside">${ICON.caret}</button>`:'')+
+      // The error mark hangs in the margin where a folder's triangle does. A folder already has
+      // its triangle there, so that turns red instead, and the feed inside shows the mark.
+      (kids?`<button class="chev${err?' bad':''}" aria-expanded="${open}" title="${err?`A feed inside has a problem: ${esc(err)}`:'Show or hide the feeds inside'}" aria-label="Show or hide the feeds inside">${ICON.caret}</button>`
+        :err?`<span class="ferr" role="img" title="${esc(err)}" aria-label="Error: ${esc(err)}">${ICON.alert}</span>`:'')+
       (mine.length?folderArt(f,mine):artHTML(f.image,f.title||f.id))+
       `<div class="txt"><b>${esc(f.title||f.id)}</b><small>`+
       `${mine.length?plural(mine.length,'feed'):plural(eps,'item')} · ${saved} downloaded`+
       `</small></div>`+
       (f.orphaned?'<span class="tag" title="No longer listed, kept because it has downloads">Gone</span>':'')+
-      (err?`<span class="tag" style="color:var(--bad)" title="${esc(err)}" aria-label="Error: ${esc(err)}">!</span>`:'')+
       `<span class="badge${unread?'':' zero'}" title="${unread} unread">${unread>999?'999+':unread}</span>`;
     el.onclick=()=>{ selectFeed(f.id); nav(false); };
     if(kids) $('.chev',el).onclick=ev=>{ ev.stopPropagation(); toggleGroup(f.id); };