fix(snapshot): Dockerfile 安装 postgresql-client-16 匹配目标 PG 版本

bookworm 默认 postgresql-client 是 15，目标数据库是 PG16
添加 PGDG 源安装 postgresql-client-16

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/services/snapshot-service/Dockerfile

@@ -17,12 +17,15 @@ FROM node:20-slim AS production
 
 WORKDIR /app
 
-# 安装系统工具: openssl, curl (健康检查), postgresql-client (pg_basebackup)
+# 安装系统工具 + PostgreSQL 16 客户端 (匹配目标数据库版本)
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    openssl \
-    curl \
-    ca-certificates \
-    postgresql-client \
+    openssl curl ca-certificates gnupg lsb-release \
+    && echo "deb http://apt.postgresql.org/pub/repos/apt $(lsb_release -cs)-pgdg main" \
+       > /etc/apt/sources.list.d/pgdg.list \
+    && curl -fsSL https://www.postgresql.org/media/keys/ACCC4CF8.asc | gpg --dearmor -o /etc/apt/trusted.gpg.d/pgdg.gpg \
+    && apt-get update && apt-get install -y --no-install-recommends \
+       postgresql-client-16 gzip \
+    && apt-get purge -y gnupg lsb-release && apt-get autoremove -y \
     && rm -rf /var/lib/apt/lists/*
 
 # 安装 MinIO 客户端 (mc)