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-ruby-client-demo/app.rb

@@ -1,51 +0,0 @@
-# frozen_string_literal: true
-
-require_relative '../kenaito-conf-ruby-client/lib/kenaito_conf'
-
-config_values = {
-  'database.host' => ENV['DATABASE_HOST'] || '192.168.1.1',
-  'database.port' => ENV['DATABASE_PORT'] || '8888',
-  'database.name' => ENV['DATABASE_NAME'] || 'xxxx',
-  'database.user' => ENV['DATABASE_USER'] || 'xxxx',
-  'database.password' => ENV['DATABASE_PASSWORD'] || 'xxxxxxxx'
-}
-
-config = KenaitoConf::Config.new(
-  base_url: ENV['KENAITO_BASE_URL'] || 'http://localhost:8080',
-  app_name: ENV['KENAITO_APP_NAME'] || 'kenaito-springboot-demo',
-  env: ENV['KENAITO_PROFILE'] || 'daily',
-  version: ENV['KENAITO_VERSION'] || 'latest',
-  token: ENV['KENAITO_TOKEN'] || '',
-  sync_interval: (ENV['KENAITO_SYNC_INTERVAL'] || '30').to_i,
-  cache_dir: ENV['KENAITO_CACHE_DIR'] || '.'
-)
-
-client = KenaitoConf::ConfigClient.new(config)
-
-client.on_change do |changed|
-  changed.each do |k, v|
-    if config_values.key?(k)
-      config_values[k] = v
-      warn "config updated: #{k} = #{v}"
-    end
-  end
-end
-
-begin
-  client.start
-  remote = client.get_all
-  config_values.each_key do |k|
-    config_values[k] = remote[k] if remote[k]
-  end
-  warn "loaded #{remote.size} configs from remote"
-rescue StandardError => e
-  warn "failed to init config client: #{e.message}"
-end
-
-puts 'Current configs:'
-config_values.each do |k, v|
-  puts "  #{k} = #{v}"
-end
-
-puts "\nListening for config changes... (press Ctrl+C to stop)"
-sleep