fix: 响应信封不再泄露派生字段 success，严格等于 {code, message, data}

- ApiResponse.isSuccess() 加 @JsonIgnore（common 引入 jackson-annotations，仅注解不含 databind）；三波以来所有响应都多带了一个契约外的 success 字段，前端解析器忽略未知字段，无破坏
- 测试补断言 $.success doesNotExist；门禁：./mvnw clean test → BUILD SUCCESS，74 测试 0 失败

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

patbond-common/pom.xml

@@ -25,6 +25,12 @@
             <groupId>jakarta.validation</groupId>
             <artifactId>jakarta.validation-api</artifactId>
         </dependency>
+        <!-- Annotations only (no databind): keeps the wire shape of the shared
+             envelope under the contract module's control. -->
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-annotations</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-test</artifactId>