feat(auth): add spring-session-jdbc 4.0.3 dependency

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/pom.xml

@@ -69,6 +69,11 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-security</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.session</groupId>
+			<artifactId>spring-session-jdbc</artifactId>
+			<version>4.0.3</version> <!-- pinned; managed by Spring Boot 4.0.6 BOM -->
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-webmvc</artifactId>