style(auth): reorganize imports and reformat controller comments

src/main/kotlin/com/msksbr/bookmgr/controller/AuthController.kt

@@ -9,6 +9,7 @@ import com.msksbr.bookmgr.template.Result
 import jakarta.servlet.http.HttpServletRequest
 import jakarta.validation.Valid
 import org.springframework.web.bind.annotation.PostMapping
+import org.springframework.web.bind.annotation.RequestAttribute
 import org.springframework.web.bind.annotation.RequestBody
 import org.springframework.web.bind.annotation.RequestMapping
 import org.springframework.web.bind.annotation.RestController
@@ -75,8 +76,12 @@ class AuthController(
     */
     @PostMapping("/logout")
     fun logout(
+        @RequestAttribute(required = false) username: String?,
         request: HttpServletRequest
     ): Result<String> {
+        if (username != null) {
+            log.info("[Auth] logout username: {}", username)
+        }
         log.info("[Auth] logout: ip={}", ipExtractor.getRealIp(request))
         log.debug("[Auth] user agent: {}", request.getHeader("User-Agent"))
         // JWT 无状态，登出只需客户端删除 token