chore: 删除多个客户端模块

移除以下未完成的客户端模块：
- C++ 客户端和 demo
- .NET 客户端和 demo
- Kotlin 客户端和 demo
- Lua 客户端和 demo
- PHP 客户端和 demo
- Ruby 客户端和 demo
- Rust 客户端和 demo

更新根目录 README.md，移除相关说明。

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

@@ -1,61 +0,0 @@
-<?php
-
-require_once __DIR__ . '/../kenaito-conf-php-client/autoload.php';
-
-use KenaitoConf\Config;
-use KenaitoConf\ConfigClient;
-
-$configValues = [
-    'database.host' => getenv('DATABASE_HOST') ?: '192.168.1.1',
-    'database.port' => getenv('DATABASE_PORT') ?: '8888',
-    'database.name' => getenv('DATABASE_NAME') ?: 'xxxx',
-    'database.user' => getenv('DATABASE_USER') ?: 'xxxx',
-    'database.password' => getenv('DATABASE_PASSWORD') ?: 'xxxxxxxx',
-];
-
-$config = new Config([
-    'baseUrl' => getenv('KENAITO_BASE_URL') ?: 'http://localhost:8080',
-    'appName' => getenv('KENAITO_APP_NAME') ?: 'kenaito-springboot-demo',
-    'env' => getenv('KENAITO_PROFILE') ?: 'daily',
-    'version' => getenv('KENAITO_VERSION') ?: 'latest',
-    'token' => getenv('KENAITO_TOKEN') ?: '',
-    'syncInterval' => (int)(getenv('KENAITO_SYNC_INTERVAL') ?: 10),
-    'cacheDir' => getenv('KENAITO_CACHE_DIR') ?: '.',
-]);
-
-$client = new ConfigClient($config);
-
-$client->onChange(function ($changed) use (&$configValues) {
-    foreach ($changed as $k => $v) {
-        if (isset($configValues[$k])) {
-            $configValues[$k] = $v;
-            error_log("config updated: {$k} = {$v}");
-        }
-    }
-});
-
-try {
-    $client->start();
-    $remote = $client->getAll();
-    foreach ($configValues as $k => &$v) {
-        if (isset($remote[$k])) {
-            $v = $remote[$k];
-        }
-    }
-    error_log("loaded " . count($remote) . " configs from remote");
-} catch (Exception $e) {
-    error_log("failed to init config client: " . $e->getMessage());
-}
-
-$port = (int)(getenv('SERVER_PORT') ?: 8084);
-
-echo "Server started on port {$port}\n";
-echo "Current configs:\n";
-foreach ($configValues as $k => $v) {
-    echo "  {$k} = {$v}\n";
-}
-
-while (true) {
-    pcntl_signal_dispatch();
-    usleep(100000);
-}