Add the browser version, a toolbar, description previews and hints

Browser version
- Self-hosted proxy (server/) that serves the web build and bridges WebSocket
  connections to Mumble servers over TLS, with a server allowlist or allow-any mode
- WebSocket transport and a browser platform layer; identities live in the browser
- npm run build:web, dev:web, proxy and test:e2e:web; proxy unit tests

Interface
- Toolbar next to mute and deafen: description editor, settings, expand or collapse all
- Channels with a description show a marker; resting on the row previews it
- Collapse all keeps channels with people open
- Hints (title tooltips) can be switched on in a new Accessibility settings tab
- New identities can set the username suggested when connecting
- Own user information tells the client address from the one the server sees

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

src/ui/ServerRail.svelte

@@ -3,6 +3,7 @@
   import { store, type SavedServer } from '../lib/settings.svelte.ts';
   import { sessions } from '../lib/session.svelte.ts';
   import { menu } from '../lib/menu.svelte.ts';
+  import { desktop } from '../lib/native.ts';
   import { makeServerIcon } from '../lib/upload.ts';
 
   let { onadd, onedit, onsettings, onbrowse }:
@@ -88,7 +89,8 @@
   {#if dropIndex === store.servers.length && dragging}<div class="drop-line"></div>{/if}
   <input bind:this={iconPicker} type="file" accept="image/*" hidden onchange={pickIcon} />
   <button class="tile add" title="Add a server" onclick={onadd}><Icon name="plus" /></button>
-  <button class="tile add" title="Browse public servers" onclick={onbrowse}><Icon name="globe" /></button>
+  <!-- The public list and its pings need the desktop app -->
+  {#if desktop}<button class="tile add" title="Browse public servers" onclick={onbrowse}><Icon name="globe" /></button>{/if}
   <div class="spacer"></div>
   <button class="tile ghost" title="Settings" onclick={onsettings}><Icon name="settings" /></button>
 </nav>