⚡️(frontend) apply frugal constraint to the active meeting audio track

Apply the `VOICE_AUDIO_CONSTRAINTS` to the audio track used during
the active meeting to reduce bandwidth usage.

* Originally proposed by trummerschlunk to reduce bandwidth, but
  previously restricted to the join screen preview.
* Backport the standard voice constraints (48 kHz sample rate,
  mono channel, 16-bit sample size) to the active call session, as
  requested by the BBBA team.

src/frontend/src/features/rooms/components/Conference.tsx

@@ -43,6 +43,7 @@ import { useSnapshot } from 'valtio'
 import { userPreferencesStore } from '@/stores/userPreferences'
 import { userStore } from '@/stores/user'
 import { WatchMediaDeviceErrors } from './WatchMediaDeviceErrors'
+import { VOICE_AUDIO_CONSTRAINTS } from '@/features/rooms/livekit/utils/constants'
 
 export const Conference = ({
   roomId,
@@ -115,6 +116,7 @@ export const Conference = ({
       },
       audioCaptureDefaults: {
         deviceId: userConfig.audioDeviceId ?? undefined,
+        ...VOICE_AUDIO_CONSTRAINTS,
       },
       audioOutput: {
         deviceId: userConfig.audioOutputDeviceId ?? undefined,

src/frontend/src/features/rooms/livekit/hooks/useJoinTracks.ts

@@ -18,6 +18,7 @@ import {
   noteDeviceReady,
   onMediaPermissionError,
 } from '../utils/mediaPermissions'
+import { VOICE_AUDIO_CONSTRAINTS } from '../utils/constants'
 import {
   saveAudioInputDeviceId,
   saveAudioInputEnabled,
@@ -27,16 +28,6 @@ import {
 } from '@/stores/userChoices'
 import { useSyncTrackDeviceId } from './useSyncTrackDeviceId'
 
-const VOICE_AUDIO_CONSTRAINTS = {
-  noiseSuppression: true,
-  echoCancellation: true,
-  autoGainControl: true,
-  voiceIsolation: false,
-  sampleRate: 48000,
-  channelCount: 1,
-  sampleSize: 16,
-} as const
-
 // Module-level: effect dependencies, must be referentially stable.
 const disableAudio = () => saveAudioInputEnabled(false)
 const disableVideo = () => saveVideoInputEnabled(false)

src/frontend/src/features/rooms/livekit/utils/constants.ts

@@ -0,0 +1,9 @@
+export const VOICE_AUDIO_CONSTRAINTS = {
+  noiseSuppression: true,
+  echoCancellation: true,
+  autoGainControl: true,
+  voiceIsolation: false,
+  sampleRate: 48000,
+  channelCount: 1,
+  sampleSize: 16,
+} as const