feat: 新增 C++ 和 Rust 客户端 SDK 及 Docker 构建支持

- 新增 kenaito-conf-cpp-client / kenaito-conf-rust-client 及对应 demo
- 新增 Dockerfile.cpp / Dockerfile.rust
- README 目录结构补充 C++/Rust 客户端
- README_DOCKERFILE 补充 Windows docker run 命令，新增 C++/Rust 段落

Dockerfile.cpp

@@ -0,0 +1,36 @@
+# Build stage
+FROM alpine:3.20 AS build
+
+WORKDIR /src
+
+# Install build dependencies
+RUN apk add --no-cache \
+    build-base \
+    cmake \
+    curl-dev \
+    git
+
+# Copy client library
+COPY kenaito-conf-cpp-client/ ./kenaito-conf-cpp-client/
+
+# Copy demo project
+COPY kenaito-conf-cpp-client-demo/ ./kenaito-conf-cpp-client-demo/
+
+# Build
+WORKDIR /src/kenaito-conf-cpp-client-demo
+RUN mkdir build && cd build && \
+    cmake .. && \
+    make
+
+# Runtime stage
+FROM alpine:3.20
+
+WORKDIR /app
+
+# Install runtime dependencies
+RUN apk add --no-cache libcurl libstdc++ libgcc
+
+# Copy binary
+COPY --from=build /src/kenaito-conf-cpp-client-demo/build/demo /app/demo
+
+ENTRYPOINT ["./demo"]