feat: 添加主页组件并设为默认首页

- 新增 HomePage.vue 主页组件 (玻璃态设计风格)
- GlobalSidebar logo 改为可点击跳转主页
- 默认页面从 writer 改为 home
- 新增玻璃态 CSS 变量支持

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/GlobalSidebar.vue

@@ -1,13 +1,18 @@
 <template>
   <aside class="sidebar">
     <!-- Logo/Home -->
-    <div class="sidebar-logo" title="AI 写作工坊">
+    <button
+      class="sidebar-logo"
+      :class="{ active: currentPage === 'home' }"
+      title="主页"
+      @click="switchPage('home')"
+    >
       <svg width="32" height="32" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg">
         <path d="M12 2L2 7L12 12L22 7L12 2Z" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
         <path d="M2 17L12 22L22 17" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
         <path d="M2 12L12 17L22 12" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
       </svg>
-    </div>
+    </button>
 
     <!-- 导航项 -->
     <nav class="sidebar-nav">
@@ -99,6 +104,10 @@ const switchPage = (page) => {
   margin-bottom: var(--space-8);
   color: var(--accent-primary);
   transition: all var(--transition-normal);
+  background: transparent;
+  border: none;
+  border-radius: var(--radius-lg);
+  cursor: pointer;
 }
 
 .sidebar-logo:hover {
@@ -106,6 +115,10 @@ const switchPage = (page) => {
   transform: scale(1.05);
 }
 
+.sidebar-logo.active {
+  background: var(--info-bg);
+}
+
 .sidebar-logo svg {
   width: 100%;
   height: 100%;