feat: desktop sidebar collapse and hidden folder scrollbar

frontend/src/App.vue

@@ -35,6 +35,7 @@ const error = ref('')
 const notice = ref('')
 const loading = ref(false)
 const mobileSidebar = ref(false)
+const sidebarCollapsed = ref(false)
 const mobileDetail = ref(false)
 const mobileMore = ref(false)
 const moreSettingsOpen = ref(false)
@@ -50,6 +51,15 @@ const taskSwipeStart = ref<{ id: string; x: number; y: number } | null>(null)
 const taskSwipeOffsets = ref<Record<string, number>>({})
 let suppressTaskClickId = ''
 
+function toggleSidebar() {
+  const compact = window.matchMedia('(max-width: 930px)').matches
+  if (compact) {
+    mobileSidebar.value = !mobileSidebar.value
+  } else {
+    sidebarCollapsed.value = !sidebarCollapsed.value
+  }
+}
+
 const modalVisible = ref(false)
 const modalTitle = ref('')
 const modalLabel = ref('')
@@ -401,7 +411,7 @@ onMounted(bootstrap)
       <small v-if="error" role="alert">{{ error }}</small>
     </section>
   </div>
-  <div v-else class="shell">
+  <div v-else class="shell" :class="{ 'sidebar-collapsed': sidebarCollapsed }">
     <div v-if="mobileSidebar || mobileDetail" class="scrim" @click="mobileSidebar=false;mobileDetail=false" />
     <aside class="sidebar" :class="{ open: mobileSidebar }">
       <div class="brand-row"><div class="brand small">do<span>do</span></div><button class="icon mobile-only" aria-label="关闭菜单" @click="mobileSidebar=false"><X /></button></div>
@@ -430,7 +440,7 @@ onMounted(bootstrap)
 
     <main>
       <header class="topbar">
-        <button class="icon mobile-only" aria-label="打开菜单" @click="mobileSidebar=true"><Menu /></button>
+        <button class="icon" :aria-label="(sidebarCollapsed ? '展开' : '收起') + '菜单'" :aria-expanded="sidebarCollapsed ? 'false' : 'true'" @click="toggleSidebar"><Menu /></button>
         <div><h1>{{ activeName }}</h1></div>
         <label v-if="['tasks','today','upcoming','trash'].includes(activeView)" class="search"><Search/><input v-model="query" placeholder="搜索任务…" aria-label="搜索任务"><kbd>⌘ K</kbd></label>
       </header>