feat(call): per-participant volume up to 200% via WebAudio gain

HTMLMediaElement.volume caps at 1.0, so boosting a quiet peer past
100% needs an explicit GainNode in the output chain. New
remoteAudioPipelines module owns one AudioContext + GainNode per
remote audio track; attachTrack / detachTrack now create and tear
down the pipeline alongside the LiveKit element.

Once a track is on the WebAudio path its direct output is diverted
(createMediaElementSource semantics), so audio.muted / volume can't
drive output anymore. Deafen, watch-state, manual screen-share mute
and per-user volume are collapsed into one effective-gain formula
that gets recomputed on every state flip — the effect subscribes to
both participantVolumes and screenShareVolumes for live slider drags.

Slider ranges updated to 0–200% across:
- ParticipantVolumeMenu (per-user right-click menu)
- ParticipantsPopover (in-call participant list)
- ScreenShareContextMenu (per-share right-click)

Values above 100% render the percentage in amber as a soft hint that
clipping is possible. Clamp in both volume stores extended to [0, 2]
so persisted values survive.

setAudioOutputDevice now additionally routes via
AudioContext.setSinkId (Chrome 115+) for the WebAudio graph; the
HTMLAudioElement.setSinkId fallback stays for older runtimes.

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

apps/desktop/src/components/ParticipantVolumeMenu.tsx

@@ -16,7 +16,7 @@ interface Props {
 }
 
 const MENU_W = 240;
-const MENU_H = 84;
+const MENU_H = 96;
 
 export function ParticipantVolumeMenu({
   userId,
@@ -63,14 +63,20 @@ export function ParticipantVolumeMenu({
     >
       <div className="mb-2 flex items-center justify-between gap-2 text-xs">
         <span className="truncate font-semibold text-fg">{displayName}</span>
-        <span className="tabular-nums text-fg-muted">
+        <span
+          className={
+            'tabular-nums ' + (volume > 1 ? 'text-amber-500' : 'text-fg-muted')
+          }
+        >
           {Math.round(volume * 100)}%
         </span>
       </div>
+      {/* Up to 200% via WebAudio gain. Values above 100% can clip on loud
+          mics — the amber count-up hints at that without a verbose warning. */}
       <input
         type="range"
         min={0}
-        max={1}
+        max={2}
         step={0.01}
         value={volume}
         onChange={(e) => {
@@ -81,6 +87,11 @@ export function ParticipantVolumeMenu({
         aria-label={'Lautstärke ' + displayName}
         className="w-full accent-accent"
       />
+      <div className="mt-1 flex justify-between text-[10px] text-fg-muted">
+        <span>0%</span>
+        <span className="tabular-nums">100%</span>
+        <span>200%</span>
+      </div>
     </div>,
     document.body,
   );