Initial commit: docker-compose-updater

Go 项目，包含：
- 服务端 updater：两阶段协议，ECDSA 签名验证，AES-GCM 加密
- 发送端 dcu-send：Gitea Action CLI
- internal/auth：加解密/签名/会话管理
- internal/docker：Docker CLI 容器查找/拉取/重建
- action/：Gitea Action 定义
- deploy/Dockerfile：多阶段构建
- .gitea/workflows/build.yaml：CI/CD

deploy/Dockerfile

@@ -0,0 +1,26 @@
+# 构建阶段
+FROM golang:1.25-alpine AS builder
+WORKDIR /src
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+
+# 注入公钥
+ARG PUBLIC_KEY_BASE64
+RUN test -n "$PUBLIC_KEY_BASE64" || (echo "PUBLIC_KEY_BASE64 required" && exit 1)
+
+RUN CGO_ENABLED=0 go build \
+  -ldflags="-X main.publicKeyBase64=${PUBLIC_KEY_BASE64}" \
+  -o /updater ./cmd/updater
+
+# 运行阶段
+FROM alpine:3.20
+RUN apk add --no-cache \
+  docker-cli \
+  docker-cli-compose \
+  ca-certificates \
+  tzdata
+
+COPY --from=builder /updater /usr/local/bin/updater
+EXPOSE 8080
+ENTRYPOINT ["updater"]