优化后台界面与无操作退出体验

frontend/src/App.vue

@@ -1,18 +1,16 @@
 <template>
-  <div class="app-shell" :class="{ 'app-locked': session.locked }">
+  <div class="app-shell">
     <router-view />
-    <LockScreenModal v-if="session.locked" />
+    <SessionTimeoutPrompt />
   </div>
   <!-- TODO: 预留聚合接口页面：/study/{id}/overview /subjects/{id}/detail /sites/{id}/summary -->
 </template>
 
 <script setup lang="ts">
-import { useSessionStore } from "./store/session";
 import { initSessionManager } from "./session/sessionManager";
-import LockScreenModal from "./components/LockScreenModal.vue";
+import SessionTimeoutPrompt from "./components/SessionTimeoutPrompt.vue";
 
 initSessionManager();
-const session = useSessionStore();
 </script>
 
 <style scoped>
@@ -20,9 +18,4 @@ const session = useSessionStore();
   min-height: 100vh;
   min-height: 100dvh;
 }
-
-.app-locked {
-  pointer-events: none;
-  user-select: none;
-}
 </style>