feat(call): integrate LiveKit for voice and video calling

Replace the manual WebRTC signaling implementation with LiveKit SFU. This includes:
- Adding LiveKit service, handler, and configuration.
- Updating Docker Compose to include LiveKit server, Redis, and PostgreSQL.
- Refactoring `CallService` and `WSHandler` to support LiveKit room readiness instead of raw SDP/ICE relaying.
- Adding new API endpoints for LiveKit token generation and webhooks.
- Removing deprecated WebRTC configuration and manual signaling DTOs.

docker-compose.yml

@@ -55,6 +55,58 @@ services:
       timeout: 20s
       retries: 3
 
+  # LiveKit SFU Server (voice/video calling)
+  livekit:
+    image: livekit/livekit-server:v1.9.5
+    container_name: livekit
+    ports:
+      - "7880:7880"   # HTTP (token, webhooks, dashboard)
+      - "7881:7881"   # TCP/TURN fallback
+      - "7882:7882"   # UDP media
+    volumes:
+      - ./configs/livekit.yaml:/etc/livekit.yaml
+    command: --config /etc/livekit.yaml --node-ip=127.0.0.1
+    depends_on:
+      livekit-redis:
+        condition: service_started
+      livekit-postgres:
+        condition: service_healthy
+    restart: unless-stopped
+
+  # LiveKit Redis (required for distributed coordination)
+  livekit-redis:
+    image: redis:7-alpine
+    container_name: livekit_redis
+    ports:
+      - "6380:6379"
+    volumes:
+      - livekit_redis_data:/data
+    healthcheck:
+      test: ["CMD", "redis-cli", "ping"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+    restart: unless-stopped
+
+  # LiveKit PostgreSQL (required for room/participant state)
+  livekit-postgres:
+    image: postgres:16-alpine
+    container_name: livekit_postgres
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_PASSWORD: postgres
+      POSTGRES_DB: livekit
+    ports:
+      - "5433:5432"
+    volumes:
+      - livekit_pg_data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U postgres -d livekit"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+    restart: unless-stopped
+
   app:
     build:
       context: .
@@ -76,3 +128,5 @@ volumes:
   # postgres_data:
   # redis_data:
   minio_data:
+  livekit_redis_data:
+  livekit_pg_data: