refactor: 迁移 DocumentsPanel.vue - SVG 图标替代 emoji

完成内容:
- 导入 IconLibrary 组件
- 替换头部标题图标 (folder)
- 替换空状态图标 (document)
- 替换操作按钮图标 (edit, copy, history, trash)
- 优化按钮样式 (flexbox, gap, 居中对齐)
- 空状态使用带背景的图标容器
- 删除按钮添加 aria-label

Emoji 数量: 6 → 0
Co-Authored-By: Claude <noreply@anthropic.com>

src/components/DocumentsPanel.vue

@@ -3,7 +3,8 @@
     <!-- 头部 -->
     <header class="docs-header">
       <h1 class="docs-header-title">
-        <span style="font-size: var(--text-xl)">📂</span> 文稿管理
+        <IconLibrary name="folder" :size="20" />
+        <span>文稿管理</span>
       </h1>
       <span class="badge badge-primary">Pro版</span>
     </header>
@@ -31,7 +32,9 @@
     <!-- 文稿列表 -->
     <div class="docs-list">
       <div v-if="filteredDocuments.length === 0" class="text-center text-muted py-8">
-        <span style="font-size: var(--text-2xl); display: block; margin-bottom: var(--space-2)">📄</span>
+        <div class="w-16 h-16 flex items-center justify-center rounded-xl bg-slate-800/50 border border-slate-700 mx-auto mb-3 opacity-40">
+          <IconLibrary name="document" :size="32" />
+        </div>
         <p class="text-sm">暂无文稿</p>
       </div>
 
@@ -62,27 +65,31 @@
       <div class="flex gap-2">
         <button
           @click="openDocument"
-          class="action-btn primary"
+          class="action-btn primary flex items-center justify-center gap-1.5"
         >
-          📝 编辑
+          <IconLibrary name="edit" :size="14" />
+          <span>编辑</span>
         </button>
         <button
           @click="duplicateDocument"
-          class="action-btn secondary"
+          class="action-btn secondary flex items-center justify-center gap-1.5"
         >
-          📋 复制
+          <IconLibrary name="copy" :size="14" />
+          <span>复制</span>
         </button>
         <button
           @click="toggleVersionPanel"
-          class="action-btn success"
+          class="action-btn success flex items-center justify-center gap-1.5"
         >
-          🕰️ 版本
+          <IconLibrary name="history" :size="14" />
+          <span>版本</span>
         </button>
         <button
           @click="confirmDelete"
-          class="action-btn danger"
+          class="action-btn danger flex items-center justify-center"
+          aria-label="删除文稿"
         >
-          🗑️
+          <IconLibrary name="trash" :size="16" />
         </button>
       </div>
     </div>
@@ -116,6 +123,7 @@ import { ref, computed, onMounted } from 'vue'
 import { useAppStore } from '../stores/app'
 import { useDatabaseStore } from '../stores/database.js'
 import { storeToRefs } from 'pinia'
+import IconLibrary from './icons/IconLibrary.vue'
 
 const appStore = useAppStore()
 const dbStore = useDatabaseStore()