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>

ios/CHANGELOG.md

@@ -11,3 +11,4 @@ The iOS app, `ios/`. Format: [Keep a Changelog](https://keepachangelog.com/en/1.
 - The icon shows All Subscriptions' unread count, as the page's badge does: set when the app comes forward, after an item is marked read, and by a refresh iOS runs now and then while the app is closed, so it can be hours behind (#421).
 - Episodes kept on the phone, with the page's Keep button, play with no connection: the app fetches the file in the background, even with the app closed, and plays it from the phone; where you got to and what you finished offline is sent once the connection is back. Signing out removes them (#425).
 - A sleep timer in the player, kept by the phone, so it pauses on time with the screen locked, fading out over the last ten seconds; and an AirPlay button beside it, for another speaker or a TV (#429).
+- Presses are felt: a light tap on play, pause, flag and pull to refresh, a success on marking read, a warning with an error (#430).