fix(agent): Dockerfile agent-builder 缺少 ARG VERSION 导致 agent.version 为空

backend/Dockerfile

@@ -46,6 +46,9 @@ RUN --mount=type=cache,target=/go/pkg/mod \
 # ==================== Stage 2: Agent Builder ====================
 FROM golang:1.24-alpine AS agent-builder
 
+ARG VERSION
+ARG BUILD_TIME
+
 WORKDIR /agent
 
 ENV GOPROXY=https://goproxy.cn,direct