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-auth/pom.xml

@@ -38,6 +38,10 @@
             <groupId>cn.meowrain.aioj</groupId>
             <artifactId>aioj-backend-common-mybatis</artifactId>
         </dependency>
+        <dependency>
+            <groupId>cn.meowrain.aioj</groupId>
+            <artifactId>aioj-backend-common-security</artifactId>
+        </dependency>
 
         <!-- ==================== 工具类 ==================== -->
         <dependency>
@@ -70,26 +74,7 @@
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-oauth2-client</artifactId>
         </dependency>
-        <dependency>
-            <groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-starter-security</artifactId>
-        </dependency>
-
-        <!-- ==================== JWT ==================== -->
-        <dependency>
-            <groupId>io.jsonwebtoken</groupId>
-            <artifactId>jjwt-api</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>io.jsonwebtoken</groupId>
-            <artifactId>jjwt-impl</artifactId>
-            <scope>runtime</scope>
-        </dependency>
-        <dependency>
-            <groupId>io.jsonwebtoken</groupId>
-            <artifactId>jjwt-jackson</artifactId>
-            <scope>runtime</scope>
-        </dependency>
+        <!-- JWT 和 Spring Security 依赖已在 common-security 中包含 -->
 
         <!-- ==================== Feign 客户端 ==================== -->
         <dependency>