feat: 新增 Bash 和 Dart 客户端 SDK 及 demo

- 新增 kenaito-conf-bash-client（Bash 4.0+，依赖 curl、jq）及对应 demo
- 新增 kenaito-conf-dart-client（Dart 2.12+，空安全）及对应 demo
- 新增 Dockerfile.bash（debian:bookworm-slim）和 Dockerfile.dart（dart:3.5）
- README 技术栈和项目结构补充 Bash、Dart 客户端
- README_EN.md 同步更新
- README_DOCKERFILE.md 补充 Bash、Dart 构建命令
- 修复 Bash 客户端 curl 2>&1 混入 stderr 导致响应解析失败
- 修复 Dart 客户端 latest.fetch.timestamp 类型转换兼容 string/num

Dockerfile.bash

@@ -0,0 +1,17 @@
+FROM debian:bookworm-slim
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    bash curl jq ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /kenaito-conf-bash-client-demo
+
+# Copy client library
+COPY kenaito-conf-bash-client/ /kenaito-conf-bash-client/
+
+# Copy demo
+COPY kenaito-conf-bash-client-demo/app.sh /kenaito-conf-bash-client-demo/app.sh
+
+RUN chmod +x app.sh
+
+ENTRYPOINT ["bash", "app.sh"]