feat(call): Discord-style polish pass (groups A-C)

A — Call core:
- Deafen now implies mute + remembers pre-deafen mic state so un-deafen
  restores it (Discord-parity). Peers still see the headphones-off +
  mic-off badges in sync via the existing data-channel broadcast.
- Self-join sound fires on the local peer's r.connect() too, not just
  on remote ParticipantConnected, so the user gets the "I'm in" cue.
- New CallState.reconnecting holds the UI steady when LiveKit drops the
  signaling socket and retries; duration keeps ticking, status label
  switches to "Verbinde neu…". Full teardown only on terminal
  Disconnected (after LK gives up).
- joinActiveCall falls back to connected after 5s if no peer arrived —
  avoids hanging in "Verbinde…" when peers left the room mid-rejoin.

B — Ringtone:
- Oscillator base gain up (incoming 0.22 -> 0.4, outgoing 0.14 -> 0.22)
  so the default pattern survives laptop speakers + background music.
- New ringtoneVolume slider in Settings, default 0.9, live-applies to
  both the oscillator fallback and the custom-file <audio> element.

C — Participant tile:
- Split the speaking indicator: video tiles get the emerald border +
  inset glow; audio tiles rely on the existing avatar pulse. No more
  double-chrome when someone talks in grid/focus view.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop/src/components/CallParticipantTile.tsx

@@ -75,7 +75,13 @@ export function CallParticipantTile(props: ParticipantTileProps) {
   } = props;
 
   const small = size === 'small';
-  const borderClass = speaking
+  // Split the speaking indicator per-mode so we don't stack a tile border
+  // + inset glow on top of the avatar pulse (visual double-chrome). Video
+  // tiles get the border (the avatar is hidden behind the stream so the
+  // pulse wouldn't be visible anyway); audio tiles rely on the avatar
+  // pulse rendered inside AudioContent.
+  const videoSpeaking = speaking && video;
+  const borderClass = videoSpeaking
     ? 'border-emerald-500 shadow-[0_0_0_2px_rgba(22,163,74,0.25)] dark:border-emerald-400'
     : focused
       ? 'border-accent'
@@ -98,9 +104,10 @@ export function CallParticipantTile(props: ParticipantTileProps) {
         <AudioContent {...props} small={small} />
       )}
 
-      {/* Speaking indicator visible regardless of content type (video or
-          audio). z-10 ensures it sits above the video element. */}
-      {speaking && (
+      {/* Video-only speaking indicator. Audio tiles use the avatar pulse
+          from AudioContent so we don't double-render chrome. z-10 keeps
+          it above the video element. */}
+      {videoSpeaking && (
         <span
           aria-hidden="true"
           className="pointer-events-none absolute inset-0 z-10 rounded-[14px] border-[3px] border-emerald-400 shadow-[inset_0_0_18px_rgba(34,197,94,0.55)]"