feat(mpc-system): 添加 debug 命令用于故障排查

新增 debug 命令，显示以下信息：
- 环境变量配置状态
- PostgreSQL 连接测试（使用 mpc.env 中的密码）
- Redis 连接测试
- RabbitMQ 状态检查
- 端口监听状态（5432, 6379, 5672, 50051, 50052, 8080）
- 各服务最近 10 条日志
- 手动测试命令提示

使用方法：
  sudo ./scripts/deploy.sh debug

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/mpc-system/scripts/deploy.sh

@@ -542,6 +542,97 @@ reconfigure() {
     log_info "Restart services with: $0 restart"
 }
 
+# ============================================
+# Debug Command (troubleshooting)
+# ============================================
+debug() {
+    echo ""
+    echo "============================================"
+    echo "MPC-System Debug Information"
+    echo "============================================"
+    echo ""
+
+    # Load environment variables
+    if [ -f "$CONFIG_DIR/mpc.env" ]; then
+        source "$CONFIG_DIR/mpc.env"
+        log_info "Loaded environment from $CONFIG_DIR/mpc.env"
+    else
+        log_error "Environment file not found: $CONFIG_DIR/mpc.env"
+        return 1
+    fi
+
+    echo ""
+    echo "=== Environment Variables ==="
+    echo "MPC_DATABASE_HOST: ${MPC_DATABASE_HOST:-NOT SET}"
+    echo "MPC_DATABASE_PORT: ${MPC_DATABASE_PORT:-NOT SET}"
+    echo "MPC_DATABASE_USER: ${MPC_DATABASE_USER:-NOT SET}"
+    echo "MPC_DATABASE_PASSWORD: ${MPC_DATABASE_PASSWORD:+SET (hidden)}"
+    echo "MPC_DATABASE_DBNAME: ${MPC_DATABASE_DBNAME:-NOT SET}"
+    echo "SESSION_COORDINATOR_ADDR: ${SESSION_COORDINATOR_ADDR:-NOT SET}"
+    echo "MESSAGE_ROUTER_ADDR: ${MESSAGE_ROUTER_ADDR:-NOT SET}"
+    echo ""
+
+    echo "=== PostgreSQL Connection Test ==="
+    local DB_USER="${MPC_DATABASE_USER:-mpc_user}"
+    local DB_PASS="${MPC_DATABASE_PASSWORD:-}"
+    local DB_NAME="${MPC_DATABASE_DBNAME:-mpc_system}"
+    local DB_HOST="${MPC_DATABASE_HOST:-localhost}"
+
+    # Test PostgreSQL connection with password
+    echo "Testing connection to PostgreSQL..."
+    if PGPASSWORD="$DB_PASS" psql -h 127.0.0.1 -U "$DB_USER" -d "$DB_NAME" -c "SELECT 1;" > /dev/null 2>&1; then
+        echo "  PostgreSQL connection: ${GREEN}OK${NC}"
+    else
+        echo "  PostgreSQL connection: ${RED}FAILED${NC}"
+        echo ""
+        echo "  Trying with verbose output:"
+        PGPASSWORD="$DB_PASS" psql -h 127.0.0.1 -U "$DB_USER" -d "$DB_NAME" -c "SELECT 1;" 2>&1 || true
+        echo ""
+        echo "  Check pg_hba.conf authentication method:"
+        cat /etc/postgresql/*/main/pg_hba.conf 2>/dev/null | grep -v "^#" | grep -v "^$" | head -10
+    fi
+    echo ""
+
+    echo "=== Redis Connection Test ==="
+    if redis-cli ping > /dev/null 2>&1; then
+        echo "  Redis connection: ${GREEN}OK${NC}"
+    else
+        echo "  Redis connection: ${RED}FAILED${NC}"
+    fi
+    echo ""
+
+    echo "=== RabbitMQ Connection Test ==="
+    if rabbitmqctl status > /dev/null 2>&1; then
+        echo "  RabbitMQ status: ${GREEN}OK${NC}"
+    else
+        echo "  RabbitMQ status: ${RED}FAILED${NC}"
+    fi
+    echo ""
+
+    echo "=== Port Listening Status ==="
+    echo "  PostgreSQL (5432): $(ss -tlnp | grep ':5432' > /dev/null && echo 'LISTENING' || echo 'NOT LISTENING')"
+    echo "  Redis (6379): $(ss -tlnp | grep ':6379' > /dev/null && echo 'LISTENING' || echo 'NOT LISTENING')"
+    echo "  RabbitMQ (5672): $(ss -tlnp | grep ':5672' > /dev/null && echo 'LISTENING' || echo 'NOT LISTENING')"
+    echo "  Session Coordinator gRPC (50051): $(ss -tlnp | grep ':50051' > /dev/null && echo 'LISTENING' || echo 'NOT LISTENING')"
+    echo "  Message Router gRPC (50052): $(ss -tlnp | grep ':50052' > /dev/null && echo 'LISTENING' || echo 'NOT LISTENING')"
+    echo "  Account Service HTTP (8080): $(ss -tlnp | grep ':8080' > /dev/null && echo 'LISTENING' || echo 'NOT LISTENING')"
+    echo ""
+
+    echo "=== Service Error Logs (last 10 lines) ==="
+    for service in mpc-session-coordinator mpc-message-router mpc-server-party-1 mpc-account; do
+        echo ""
+        echo "--- $service ---"
+        journalctl -u "$service" --no-pager -n 10 2>/dev/null || echo "No logs available"
+    done
+    echo ""
+
+    echo "=== Manual Test Command ==="
+    echo "Run this command to manually test a service:"
+    echo ""
+    echo "  sudo -u $MPC_USER bash -c 'source $CONFIG_DIR/mpc.env && $BIN_DIR/session-coordinator'"
+    echo ""
+}
+
 # ============================================
 # Uninstall Command
 # ============================================
@@ -588,6 +679,9 @@ case "${1:-}" in
     reconfigure)
         reconfigure
         ;;
+    debug)
+        debug
+        ;;
     start)
         start_services
         ;;
@@ -609,12 +703,13 @@ case "${1:-}" in
     *)
         echo "MPC-System Deployment Script"
         echo ""
-        echo "Usage: $0 {install|build|reconfigure|start|stop|restart|status|logs|uninstall}"
+        echo "Usage: $0 {install|build|reconfigure|debug|start|stop|restart|status|logs|uninstall}"
         echo ""
         echo "Commands:"
         echo "  install     - Install system dependencies (Go, PostgreSQL, Redis, RabbitMQ)"
         echo "  build       - Build services and configure infrastructure"
         echo "  reconfigure - Reconfigure PostgreSQL/Redis/RabbitMQ (fix auth issues)"
+        echo "  debug       - Show debug information and test connections"
         echo "  start       - Start all MPC services"
         echo "  stop        - Stop all MPC services"
         echo "  restart     - Restart all MPC services"
@@ -630,6 +725,7 @@ case "${1:-}" in
         echo "  $0 status        # Check status"
         echo ""
         echo "Troubleshooting:"
+        echo "  $0 debug         # Show debug info and test DB connection"
         echo "  $0 reconfigure   # Fix database authentication issues"
         echo "  $0 restart       # Then restart services"
         echo ""