refactor(deploy): separate Dev/UAT into independent full-stack environments

- Each environment now runs its own PB + LiveKit + Voice Token + frontend
- UAT LiveKit: 7890, Voice Token: 7893 (separate from Dev 7880/7883)
- Remove docker-compose.backend.yml, merge into dev compose
- Delete duplicate bulletin migration files that caused PB crash on startup
- Update CLAUDE.md, nginx configs, and .env files accordingly

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docker-compose.dev.yml

@@ -1,4 +1,55 @@
 services:
+  pocketbase-dev:
+    image: ghcr.io/muchobien/pocketbase:0.22.4
+    container_name: gamegroup-pb
+    ports:
+      - "8090:8090"
+    volumes:
+      - ./backend/pb_data:/pb_data
+      - ./backend/pb_migrations:/pb_migrations
+      - ./backend/pb_hooks:/pb_hooks
+    environment:
+      - GO_ENV=production
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider", "http://localhost:8090/api/health"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 40s
+    networks:
+      - gamegroup-net
+
+  livekit-dev:
+    image: livekit/livekit-server:v1.10
+    container_name: gamegroup-livekit-dev
+    ports:
+      - "7880:7880"
+      - "7881:7881/udp"
+      - "7882:7882/udp"
+    environment:
+      LIVEKIT_KEYS: "APIyxZGQjM2: secretNmU4ZDU3YjA0OWIxNDM4YjhlNWY3YTFjZGUzOWRi"
+    command: --dev --node-ip 192.168.1.14
+    restart: unless-stopped
+    networks:
+      - gamegroup-net
+
+  voice-token-dev:
+    build:
+      context: ./backend/voice-token-service
+    container_name: gamegroup-voice-token-dev
+    ports:
+      - "7883:7882"
+    environment:
+      - LIVEKIT_API_KEY=APIyxZGQjM2
+      - LIVEKIT_API_SECRET=secretNmU4ZDU3YjA0OWIxNDM4YjhlNWY3YTFjZGUzOWRi
+      - PB_URL=http://gamegroup-pb:8090
+    restart: unless-stopped
+    depends_on:
+      - pocketbase-dev
+    networks:
+      - gamegroup-net
+
   frontend-dev:
     build:
       context: ./frontend
@@ -11,6 +62,8 @@ services:
     environment:
       - NODE_ENV=production
     restart: unless-stopped
+    depends_on:
+      - pocketbase-dev
     networks:
       - gamegroup-net