refactor: 重构安全架构，提取通用安全模块到common-security

- 将JwtAuthenticationFilter、JwtUtil、JwtProperties从auth服务移至common-security模块
- 新增common-security通用安全模块，提供JWT认证、权限验证等核心安全功能
- 重命名SecurityConfiguration为AuthSecurityConfiguration，使用common-security的filter
- 新增JacksonConfiguration配置类，统一JSON序列化配置
- 新增头像更新功能AvatarUpdateRequestDTO
- 移除冗余的UserLoginResponseDTO类
- 更新各服务模块的依赖配置以引入common-security模块
- 新增README.md项目说明文档

Co-Authored-By: Claude <noreply@anthropic.com>

aioj-backend-common/aioj-backend-common-core/src/main/java/cn/meowrain/aioj/backend/framework/core/jackson/JacksonConfiguration.java

@@ -0,0 +1,35 @@
+package cn.meowrain.aioj.backend.framework.core.jackson;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
+import org.springframework.boot.autoconfigure.AutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
+import org.springframework.context.annotation.Bean;
+
+/**
+ * Jackson 全局配置
+ * 解决 Long 类型在前端 JavaScript 精度丢失问题
+ */
+@AutoConfiguration
+@ConditionalOnClass(ObjectMapper.class)
+public class JacksonConfiguration {
+
+	/**
+	 * 自定义 Jackson ObjectMapper 配置
+	 * 将 Long 和 long 类型序列化为 String
+	 */
+	@Bean
+	public Jackson2ObjectMapperBuilderCustomizer jackson2ObjectMapperBuilderCustomizer() {
+		return builder -> {
+			// 注册 JavaTimeModule 处理时间类型
+			builder.modules(new JavaTimeModule());
+			
+			// Long 和 long 类型序列化为 String，避免前端精度丢失
+			builder.serializerByType(Long.class, ToStringSerializer.instance);
+			builder.serializerByType(Long.TYPE, ToStringSerializer.instance);
+		};
+	}
+
+}

aioj-backend-common/aioj-backend-common-core/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports

@@ -1,2 +1,3 @@
 cn.meowrain.aioj.backend.framework.core.banner.config.AIOJBannerAutoConfiguration
-cn.meowrain.aioj.backend.framework.core.config.WebAutoConfiguration
+cn.meowrain.aioj.backend.framework.core.config.WebAutoConfiguration
+cn.meowrain.aioj.backend.framework.core.jackson.JacksonConfiguration