feat: Spring Boot示例项目

- 基础Spring Boot配置
- Docker支持

src/main/java/com/example/demo/model/User.java

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+package com.example.demo.model;
+
+/**
+ * 用户实体类
+ * 
+ * 学习点：
+ * - JavaBean / POJO 设计模式
+ * - Lombok 可以简化 getter/setter（这里用原生写法演示）
+ */
+public class User {
+    private Long id;
+    private String name;
+    private String email;
+    private Integer age;
+
+    public User() {}
+
+    public User(Long id, String name, String email, Integer age) {
+        this.id = id;
+        this.name = name;
+        this.email = email;
+        this.age = age;
+    }
+
+    // Getters and Setters
+    public Long getId() { return id; }
+    public void setId(Long id) { this.id = id; }
+    public String getName() { return name; }
+    public void setName(String name) { this.name = name; }
+    public String getEmail() { return email; }
+    public void setEmail(String email) { this.email = email; }
+    public Integer getAge() { return age; }
+    public void setAge(Integer age) { this.age = age; }
+}

src/main/java/com/example/demo/model/UserEvent.java

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+package com.example.demo.model;
+
+import java.time.LocalDateTime;
+
+/**
+ * 用户事件 - 演示 Spring 事件机制
+ * 
+ * 学习点：
+ * - ApplicationEvent 基类
+ * - 事件驱动架构
+ * - 观察者模式
+ */
+public class UserEvent {
+    
+    public enum Type {
+        CREATED,    // 用户创建
+        UPDATED,    // 用户更新
+        DELETED,    // 用户删除
+        LOGIN       // 用户登录
+    }
+    
+    private Type type;
+    private Long userId;
+    private String userName;
+    private LocalDateTime timestamp;
+    private String detail;
+    
+    public UserEvent() {
+        this.timestamp = LocalDateTime.now();
+    }
+    
+    public UserEvent(Type type, Long userId, String userName, String detail) {
+        this.type = type;
+        this.userId = userId;
+        this.userName = userName;
+        this.detail = detail;
+        this.timestamp = LocalDateTime.now();
+    }
+    
+    // Getters and Setters
+    public Type getType() { return type; }
+    public void setType(Type type) { this.type = type; }
+    public Long getUserId() { return userId; }
+    public void setUserId(Long userId) { this.userId = userId; }
+    public String getUserName() { return userName; }
+    public void setUserName(String userName) { this.userName = userName; }
+    public LocalDateTime getTimestamp() { return timestamp; }
+    public void setTimestamp(LocalDateTime timestamp) { this.timestamp = timestamp; }
+    public String getDetail() { return detail; }
+    public void setDetail(String detail) { this.detail = detail; }
+}