feat: 新增 8 个语言客户端 SDK

- PHP 客户端 (kenaito-conf-php-client)
- .NET 客户端 (kenaito-conf-dotnet-client)
- C 客户端 (kenaito-conf-c-client)
- C++ 客户端 (kenaito-conf-cpp-client)
- Lua 客户端 (kenaito-conf-lua-client)
- Kotlin 客户端 (kenaito-conf-kotlin-client)
- Rust 客户端 (kenaito-conf-rust-client)
- Ruby 客户端 (kenaito-conf-ruby-client)

每个客户端包含完整的 SDK 实现和 demo 示例，支持：
- 配置拉取（全量/增量）
- AES-128-CBC 解密
- 本地缓存
- 变更回调
- Token 认证

更新根目录 README.md：
- 技术栈列表新增 8 种语言
- 项目结构新增 16 个目录
- 客户端接入章节新增 8 个使用示例

kenaito-conf-lua-client-demo/app.lua

@@ -0,0 +1,49 @@
+local ConfigClient = require("kenaito-conf")
+
+local config_values = {
+    ["database.host"] = os.getenv("DATABASE_HOST") or "192.168.1.1",
+    ["database.port"] = os.getenv("DATABASE_PORT") or "8888",
+    ["database.name"] = os.getenv("DATABASE_NAME") or "xxxx",
+    ["database.user"] = os.getenv("DATABASE_USER") or "xxxx",
+    ["database.password"] = os.getenv("DATABASE_PASSWORD") or "xxxxxxxx",
+}
+
+local config = {
+    baseUrl = os.getenv("KENAITO_BASE_URL") or "http://localhost:8080",
+    appName = os.getenv("KENAITO_APP_NAME") or "kenaito-springboot-demo",
+    env = os.getenv("KENAITO_PROFILE") or "daily",
+    version = os.getenv("KENAITO_VERSION") or "latest",
+    token = os.getenv("KENAITO_TOKEN") or "",
+    syncInterval = tonumber(os.getenv("KENAITO_SYNC_INTERVAL") or "30"),
+    cacheDir = os.getenv("KENAITO_CACHE_DIR") or ".",
+}
+
+local client = ConfigClient.new(config)
+
+client:on_change(function(changed)
+    for k, v in pairs(changed) do
+        if config_values[k] then
+            config_values[k] = v
+            print("config updated: " .. k .. " = " .. v)
+        end
+    end
+end)
+
+client:start()
+
+local remote = client:get_all()
+for k, v in pairs(remote) do
+    if config_values[k] then
+        config_values[k] = v
+    end
+end
+
+print("Current configs:")
+for k, v in pairs(config_values) do
+    print("  " .. k .. " = " .. v)
+end
+
+print("\nListening for config changes... (press Ctrl+C to stop)")
+while true do
+    os.execute("sleep 1")
+end