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/TabBar.vue

@@ -0,0 +1,27 @@
+<script setup lang="ts">
+import Icon from './Icon.vue'
+import { noteTitle } from './paths'
+import { closeTab, ws } from './workspace'
+</script>
+
+<template>
+  <nav class="rm-tabs" role="tablist">
+    <div
+      v-for="tab in ws.tabs"
+      :key="tab.path"
+      class="rm-tab"
+      :class="{ active: ws.active === tab.path }"
+      role="tab"
+      :aria-selected="ws.active === tab.path"
+      :title="tab.path"
+      @click="ws.active = tab.path"
+      @auxclick.prevent="$event.button === 1 && closeTab(tab.path)"
+    >
+      <span class="rm-tab-title">{{ noteTitle(tab.path) }}</span>
+      <button class="rm-tab-close" :class="{ dirty: tab.dirty }" title="关闭" @click.stop="closeTab(tab.path)">
+        <span class="rm-dirty-dot" />
+        <Icon name="close" :size="12" />
+      </button>
+    </div>
+  </nav>
+</template>