feat(voice): add WebRTC voice channels with Cloudflare TURN support

Add voice channel functionality with WebRTC peer-to-peer audio:
- Add VoiceSignalingConsumer for WebRTC signaling and peer coordination
- Add GlobalConsumer for real-time presence and voice status updates
- Add voice channel type to Channel model with current_voice_channel tracking on UserProfile
- Add voice controls UI (mute, deafen, disconnect) in status panel
- Add voice member list display in sidebar with avatar support
- Add

.env

@@ -0,0 +1,12 @@
+SECRET_KEY=poc-secret-key-not-for-production
+DEBUG=True
+DB_NAME=discord_db
+DB_USER=discord_user
+DB_PASSWORD=discord_pass
+DB_HOST=db
+DB_PORT=5432
+
+# Cloudflare Realtime TURN Configuration
+CLOUDFLARE_ACCOUNT_ID=
+CLOUDFLARE_API_TOKEN=
+CLOUDFLARE_TURN_KEY_ID=