修复部署 2

Dockerfile.backend

@@ -1,4 +1,7 @@
-FROM golang:1.26-alpine AS builder
+ARG GO_BUILDER_IMAGE=docker.m.daocloud.io/library/golang:1.26-alpine
+ARG BACKEND_RUNTIME_IMAGE=docker.m.daocloud.io/library/alpine:3.22
+
+FROM ${GO_BUILDER_IMAGE} AS builder
 
 WORKDIR /app
 
@@ -13,7 +16,7 @@ WORKDIR /app/backend
 RUN CGO_ENABLED=0 GOOS=linux go build -o /server ./cmd/server
 
 # 最终运行镜像 / Runtime image
-FROM alpine:latest
+FROM ${BACKEND_RUNTIME_IMAGE}
 
 RUN apk --no-cache add ca-certificates tzdata curl