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

kenaito-conf-cpp-client/CMakeLists.txt

@@ -0,0 +1,45 @@
+cmake_minimum_required(VERSION 3.10)
+project(kenaito-conf-cpp-client VERSION 1.0.0 LANGUAGES CXX)
+
+set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+find_package(CURL REQUIRED)
+
+# 自动下载 nlohmann/json（单头文件）
+set(JSON_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/third_party/nlohmann)
+if(NOT EXISTS ${JSON_INCLUDE_DIR}/json.hpp)
+    message(STATUS "Downloading nlohmann/json.hpp...")
+    file(MAKE_DIRECTORY ${JSON_INCLUDE_DIR})
+    file(DOWNLOAD
+        https://github.com/nlohmann/json/releases/download/v3.11.3/json.hpp
+        ${JSON_INCLUDE_DIR}/json.hpp
+        SHOW_PROGRESS
+    )
+endif()
+
+add_library(kenaito_conf_client STATIC
+    src/client.cpp
+)
+
+target_include_directories(kenaito_conf_client
+    PUBLIC
+        ${CMAKE_CURRENT_SOURCE_DIR}/include
+        ${CMAKE_CURRENT_SOURCE_DIR}/third_party
+    PRIVATE
+        ${CURL_INCLUDE_DIRS}
+)
+
+target_link_libraries(kenaito_conf_client
+    PRIVATE
+        ${CURL_LIBRARIES}
+)
+
+# Install
+install(TARGETS kenaito_conf_client
+    ARCHIVE DESTINATION lib
+)
+
+install(DIRECTORY include/kenaito_conf
+    DESTINATION include
+)