refactor: drop LeftSidebar header in favor of group rows

The "Views" header + MoreHorizontal kebab were vestigial — the Views/Folders
group rows already label themselves, and the kebab was a no-op. Swap the
group icons (Layers2 for Views, HardDrive for Folders) so the visual
hierarchy stays clear without the header.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/layout/LeftSidebar.tsx

@@ -6,11 +6,11 @@ import {
   Image,
   Star,
   Trash2,
-  MoreHorizontal,
   HardDrive,
   RefreshCw,
   Copy,
   Tag as TagIcon,
+  Layers2,
 } from 'lucide-react'
 import clsx from 'clsx'
 import { sourceFolders, library, photos as photosApi, type FolderTreeNode } from '../../services/api'
@@ -211,8 +211,8 @@ export function LeftSidebar() {
   const libraryTree: TreeItem[] = [
     {
       id: 'library',
-      label: 'Library',
+      label: 'Views',
-      icon: <HardDrive className="h-4 w-4" />,
+      icon: <Layers2 className="h-4 w-4" />,
       children: [
         { id: 'all-photos', label: 'All Photos', icon: <Image className="h-4 w-4" />, count: 0 },
         { id: 'rated', label: 'Rated', icon: <Star className="h-4 w-4" />, count: 0 },
@@ -224,7 +224,7 @@ export function LeftSidebar() {
     {
       id: 'folders',
       label: 'Folders',
-      icon: <Folder className="h-4 w-4" />,
+      icon: <HardDrive className="h-4 w-4" />,
       children: folderTree.map(folderNodeToTreeItem),
     },
   ]
@@ -403,14 +403,6 @@ export function LeftSidebar() {
 
   return (
     <div className="flex h-full flex-col bg-surface">
-      {/* Sidebar Header */}
-      <div className="flex items-center justify-between border-b border-border px-3 py-2">
-        <h2 className="text-sm font-semibold text-text">Views</h2>
-        <button className="rounded p-1 text-text-muted hover:bg-surface-2 hover:text-text">
-          <MoreHorizontal className="h-4 w-4" />
-        </button>
-      </div>
-
       {/* Tree View */}
       <div className="flex-1 overflow-y-auto py-2">
         {libraryTree.map((item) => renderTreeItem(item))}