feat(web): add Vue workspace with file tree, tabs, autosave and live sync

- Login and first-run setup screens
- File tree with inline create/rename, context menu, drag-and-drop
  move and trash with undo; all operations update the UI first and roll
  back on failure
- Tabs keep a CodeMirror state each; edits autosave after 500 ms with
  If-Match revisions, unsent edits persist in IndexedDB, and conflicts
  or remote deletions surface as banners with explicit choices
- WebSocket events sync external edits, moves and deletions into open
  tabs; reconnects trigger a full resync
- Pasted or dropped images show instantly and upload to note.assets/
- Responsive layout with a swipe-in sidebar drawer on phones
- Switch to TypeScript 6: vue-tsc does not support TypeScript 7 yet

web/src/app/Sidebar.vue

@@ -0,0 +1,48 @@
+<script setup lang="ts">
+import { ref } from 'vue'
+import Icon from './Icon.vue'
+import { basename } from './paths'
+import TrashDialog from './TrashDialog.vue'
+import { tree } from './tree'
+import TreeNode from './TreeNode.vue'
+import { createFolder, createNote, move } from './workspace'
+
+const emit = defineEmits<{ logout: [] }>()
+const trashOpen = ref(false)
+const rootDrop = ref(false)
+
+function onRootDragOver(e: DragEvent) {
+  if (!e.dataTransfer?.types.includes('application/x-rawmark-path')) return
+  e.preventDefault()
+  rootDrop.value = true
+}
+
+function onRootDrop(e: DragEvent) {
+  rootDrop.value = false
+  const src = e.dataTransfer?.getData('application/x-rawmark-path')
+  if (!src || !src.includes('/')) return
+  e.preventDefault()
+  void move(src, basename(src))
+}
+</script>
+
+<template>
+  <div class="rm-sidebar-inner">
+    <div class="rm-sidebar-head">
+      <span class="rm-brand">RawMark</span>
+      <button class="rm-icon-btn" title="新建笔记" @click="createNote('')"><Icon name="noteAdd" /></button>
+      <button class="rm-icon-btn" title="新建文件夹" @click="createFolder('')"><Icon name="folderAdd" /></button>
+    </div>
+    <div class="rm-tree" :class="{ drop: rootDrop }" @dragover="onRootDragOver" @dragleave="rootDrop = false" @drop="onRootDrop">
+      <ul class="rm-tree-list">
+        <TreeNode v-for="node in tree" :key="node.path" :node="node" :depth="0" />
+      </ul>
+      <p v-if="!tree.length" class="rm-tree-empty">还没有笔记</p>
+    </div>
+    <div class="rm-sidebar-foot">
+      <button class="rm-foot-btn" @click="trashOpen = true"><Icon name="trash" />回收站</button>
+      <button class="rm-foot-btn" @click="emit('logout')"><Icon name="logout" />退出</button>
+    </div>
+    <TrashDialog v-if="trashOpen" @close="trashOpen = false" />
+  </div>
+</template>