feat(learning-auth): add optional JWT learning flow with secure demo endpoint

pom.xml

@@ -43,6 +43,29 @@
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-validation</artifactId>
         </dependency>
+
+        <!-- 仅用于学习的可选鉴权演示（不影响主流程） -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-security</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.jsonwebtoken</groupId>
+            <artifactId>jjwt-api</artifactId>
+            <version>0.12.3</version>
+        </dependency>
+        <dependency>
+            <groupId>io.jsonwebtoken</groupId>
+            <artifactId>jjwt-impl</artifactId>
+            <version>0.12.3</version>
+            <scope>runtime</scope>
+        </dependency>
+        <dependency>
+            <groupId>io.jsonwebtoken</groupId>
+            <artifactId>jjwt-jackson</artifactId>
+            <version>0.12.3</version>
+            <scope>runtime</scope>
+        </dependency>
         
         <!-- 测试 -->
         <dependency>