refactor(call): move noise-suppression toggle out of the call bar

Default flipped to off so voice doesn't get coloured by browser NS on
first run. Users turn it on explicitly under Settings → Sprache, where
the toggle already lived before the in-call button shipped.

The in-call SparklesIcon button and all the associated wiring
(onToggleNoiseSuppression, noiseSuppression prop, local subscription
in InCallPanel) is removed. The hot-swap UX is preserved: a new
subscribeAudioSettings watcher in CallContext detects noiseSuppression
flips during an active call and re-runs setupMicPipeline so the change
takes effect without rejoining.

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

apps/desktop/src/lib/audioSettings.ts

@@ -41,7 +41,10 @@ const DEFAULTS: AudioSettings = {
   inputDeviceId: null,
   outputDeviceId: null,
   voiceThreshold: 0.03,
-  noiseSuppression: true,
+  // Off by default — browser-native NS colours voice audibly on some
+  // mics and is a frequent "why does my voice sound weird" report.
+  // Users who want it enable it explicitly in Settings → Sprache.
+  noiseSuppression: false,
   videoBackgroundBlur: false,
   ringtoneVolume: 0.9,
 };