feat(filelib): 老师端左栏导航:回收站 + 最近打开(ADR-0031)

- 回收站:listBin(祖先全活跃的已删顶点;管理员/直连 MANAGE 可见)、
  restore(与 D15 对称只清本节点,落审计)、purge(仅管理员,pathIds 枚举
  子树按深度降序分批硬删,绕过 self-FK RESTRICT)
- 最近打开:FileLibRecentVisit 表(filePath='' 兜底 PG 唯一索引),客户端
  成功打开后上报(VIEW 门禁,upsert 刷新),列表 20 条,D8/D15 可见性过滤
- 前端:/app 左栏(文件库/最近打开/回收站);RecentView/BinView;
  GridLibraryView 埋点 + navTarget 跳转(breadcrumb 建栈,role 已捎带)
- 测试:filelib-nav 集成 4 例;全套 79 例绿

hub/filelib-web/src/routes/app/+page.svelte

@@ -1,12 +1,30 @@
 <script lang="ts">
-  /** 老师端。未登录显示登录卡片;登录后是网盘式文件库浏览器。 */
+  /** 老师端。未登录显示登录卡片;登录后是带左栏导航的文件库(ADR-0031)。 */
   import { onMount } from "svelte";
   import { me, authChecked } from "$lib/stores.js";
   import { loadSession } from "$lib/session.js";
   import LoginView from "$lib/LoginView.svelte";
-  import GridLibraryView from "$lib/GridLibraryView.svelte";
+  import GridLibraryView, { type NavTarget } from "$lib/GridLibraryView.svelte";
+  import RecentView from "$lib/RecentView.svelte";
+  import BinView from "$lib/BinView.svelte";
+  import Icon from "$lib/Icon.svelte";
 
   onMount(loadSession);
+
+  type View = "library" | "recent" | "bin";
+  let view = $state<View>("library");
+  let navTarget = $state<NavTarget | null>(null);
+
+  function openFromRecent(target: NavTarget): void {
+    navTarget = target;
+    view = "library";
+  }
+
+  const tabs: ReadonlyArray<readonly [View, string, "layers" | "clock" | "trash"]> = [
+    ["library", "文件库", "layers"],
+    ["recent", "最近打开", "clock"],
+    ["bin", "回收站", "trash"],
+  ];
 </script>
 
 <svelte:head><title>文件库</title></svelte:head>
@@ -14,8 +32,29 @@
 {#if !$authChecked}
   <div class="flex h-full items-center justify-center text-ink-3">加载中…</div>
 {:else if $me}
-  <div class="flex h-full flex-col">
-    <GridLibraryView />
+  <div class="flex h-full">
+    <!-- 左栏导航(ADR-0031) -->
+    <nav class="flex w-[168px] shrink-0 flex-col gap-0.5 border-r border-line-soft bg-sidebar px-2.5 py-3.5">
+      {#each tabs as [id, label, icon] (id)}
+        <button
+          class="flex items-center gap-2.5 rounded-lg px-3 py-2 text-left text-[13px] transition {view === id
+            ? 'bg-selected font-semibold text-ink'
+            : 'text-ink-2 hover:bg-hover'}"
+          onclick={() => (view = id)}
+        >
+          <span class="text-ink-3"><Icon name={icon} size={15} /></span>
+          {label}
+        </button>
+      {/each}
+    </nav>
+
+    {#if view === "library"}
+      <GridLibraryView {navTarget} onnavigated={() => (navTarget = null)} />
+    {:else if view === "recent"}
+      <RecentView onopen={openFromRecent} />
+    {:else}
+      <BinView />
+    {/if}
   </div>
 {:else}
   <LoginView />