Add k3s cluster expansion documentation and scripts

- Complete expansion guide for 2/4/6 node scenarios
- Quick join scripts for worker and master nodes
- Health check and diagnostic scripts
- Quick reference card for common operations

php-test/schema.sql

@@ -0,0 +1,13 @@
+-- 创建数据库
+CREATE DATABASE IF NOT EXISTS test_db CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
+
+USE test_db;
+
+-- 创建测试表
+CREATE TABLE IF NOT EXISTS test_data (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    name VARCHAR(100) NOT NULL,
+    email VARCHAR(100) NOT NULL,
+    message TEXT,
+    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;