v3.4: handle-leak fix, Realtek ASIO block, device notifications, quick profile switch, hotkey announcements

Freezes the v3.4 feature set (everything since the v3.3 public release):

- Fix the receiver handle leak: the 3-second device-refresh timer reopened the
  configured ASIO driver every tick, and Realtek's ASIO driver leaks Event+Mutant
  handles on every open. Cache the ASIO probe per driver so it is opened once.
- Realtek ASIO block: detect a Realtek ASIO driver, offer once to disable it, and
  never touch it again if disabled; Options-menu toggle to reverse. Global config.
- Device hot-plug is event-driven (AudioDeviceChangeNotifier) instead of a 3s poll;
  debounced refresh, falls back to polling if registration fails.
- Quick profile switch: new global hotkey opens an NVDA-friendly popup of all
  profiles (current marked); Enter/click switches; plays a new "profile menu open"
  cue with Preferences mute + custom-sound.
- Announce assigned global hotkeys on the controls/menu items they drive (NVDA reads
  "press X anywhere"). File > Open already had Ctrl+O.
- Held-back changes folded in: config-folder migration, codec-column fix, Tailscale
  endpoint network-prune, empty-password guard, and the handle-leak diagnostics
  (ProcessSelfMeter, HandleTypeProbe).

Version bumped to 3.4.0.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

readme.html

@@ -67,6 +67,10 @@ ul, ol { padding-left: 1.4em; }
 
 <p>There is no central server, no account, and nothing stored online. The sound goes straight from one computer to the other.</p>
 
+<div class="note">
+<strong>RemSound on Android (receiver):</strong> there is a companion app that lets a phone or tablet <em>receive</em> RemSound audio &mdash; handy for listening on the move. It's a separate community project built and maintained by Aryan Choudhary, who is a screen-reader user himself and has tuned the app for TalkBack; it is not part of RemSound and is not maintained by us. Get the signed app from its releases page (download the latest <strong>app-release.apk</strong>): <a href="https://github.com/aryanchoudharypro/RemSoundAndroid/releases">RemSound Android &mdash; Releases</a>.
+</div>
+
 <h2 id="quick-start">2. Quick start</h2>
 
 <p>Let's assume you and a friend both have RemSound running, and that your two computers can reach each other on the network (the same Wi-Fi, the same Tailscale account, and so on).</p>