Update SproutGate

sproutgate-backend/Dockerfile

@@ -1,11 +1,9 @@
-FROM golang:1.20-alpine AS builder
-
-WORKDIR /app
-COPY go.mod go.sum ./
-RUN go mod download
-
-COPY . .
-RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o /out/sproutgate-backend .
+# 默认：只复制本机/CI 已构建的 Linux amd64 二进制，不在镜像里执行 go build。
+# 1) 在 sproutgate-backend 目录执行: build-linux-amd64.bat
+#    或:  set CGO_ENABLED=0&& set GOOS=linux&& set GOARCH=amd64&& go build -trimpath -ldflags="-s -w" -o dist\sproutgate-backend .
+# 2) 再:  docker compose build
+#
+# 若必须在 Docker 里从源码编译，请用:  docker build -f Dockerfile.build -t ... .
 
 FROM alpine:3.19
 RUN apk add --no-cache ca-certificates tzdata
@@ -14,8 +12,7 @@ WORKDIR /app
 ENV PORT=8080
 ENV DATA_DIR=/data
 
-COPY --from=builder /out/sproutgate-backend /usr/local/bin/sproutgate-backend
-COPY API_DOCS.md /app/API_DOCS.md
+COPY dist/sproutgate-backend /usr/local/bin/sproutgate-backend
 
 EXPOSE 8080
 VOLUME ["/data"]