iOS: presses are felt (#430)

The page asks the app for a haptic ({t:"haptic", kind}) and the app
plays the phone's own. A light tap for play, pause, flag and pull to
refresh; the system's success for marking read, one item or all; its
warning with an error toast. A browser has no host to ask, and an
older app ignores the message, so there is nothing to gate.

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

web/src/gestures.ts

@@ -156,7 +156,7 @@ document.addEventListener('touchend', () => {
   if(!g) return;
   if(g.pane === 'list'){
     pullShow(0);
-    if(g.dy >= PULL) refreshFeed();
+    if(g.dy >= PULL){ haptic('tap'); refreshFeed(); }
     return;
   }
   const i = S.entries.findIndex(x => entryKey(x) === S.sel);