feat: 内容数据迁移至数据库，合规审查全链路打通

- 文章 HTML 存储从文件系统迁移至 articles 表，删除 releases 目录
- 合规审查从 DB 读取 HTML，审查结果写回 DB，通过后自动推进至待发布
- 新增 todayCount 筛选按钮，与系统概览统计数据一致
- 全屏预览修复：提升 z-index 超过侧边栏，添加退出全屏/关闭按钮
- 统一 '优化' → '审查' 命名，消除前后端术语不一致
- 调度器创作完成后自动触发审查（生成 → 审查 → 待发布）
- 清理旧备份/调试文件、过期大纲和研究笔记

platform/frontend/assets.html

@@ -5,23 +5,14 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>宇之然内容创作平台 - 素材库</title>
     <link rel="stylesheet" href="element-plus.css">
+    <link rel="stylesheet" href="theme-modern.css">
     <style>
         * { margin: 0; padding: 0; box-sizing: border-box; }
         body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif; background: #f5f7fa; }
-        .navbar { background: linear-gradient(135deg, #2563eb 0%, #1d4ed8 100%); color: white; padding: 16px 24px; box-shadow: 0 2px 8px rgba(0,0,0,0.1); }
-        .navbar-content { display: flex; justify-content: space-between; align-items: center; max-width: 1400px; margin: 0 auto; }
-        .navbar-title { font-size: 20px; font-weight: 600; }
-        .navbar-user { display: flex; align-items: center; gap: 16px; }
-        .user-info { display: flex; align-items: center; gap: 8px; }
-        .avatar { width: 32px; height: 32px; border-radius: 50%; background: rgba(255,255,255,0.2); display: flex; align-items: center; justify-content: center; font-size: 14px; }
         .main-content { display: flex; flex: 1; max-width: 1400px; margin: 0 auto; }
-        .sidebar { width: 180px; background: white; padding: 12px; box-shadow: 2px 0 8px rgba(0,0,0,0.05); }
         .content-area { flex: 1; padding: 24px; overflow-y: auto; }
-        .card { background: white; border-radius: 12px; padding: 24px; margin-bottom: 24px; box-shadow: 0 2px 8px rgba(0,0,0,0.08); }
-        .mobile-nav { display: none; position: fixed; bottom: 0; left: 0; right: 0; background: white; box-shadow: 0 -2px 8px rgba(0,0,0,0.1); padding: 8px 0; z-index: 1000; }
+        .card { background: white; border-radius: 16px; padding: 24px; margin-bottom: 24px; box-shadow: 0 2px 12px rgba(0,0,0,0.06); overflow-x: auto; transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1); }
         @media (max-width: 768px) {
-            .sidebar { display: none; }
-            .mobile-nav { display: flex; }
             .content-area { padding: 16px; padding-bottom: 80px; }
         }
         .asset-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 16px; }
@@ -46,7 +37,7 @@
         <div class="main-content">
             <main class="content-area">
                 <h2 style="font-size: 24px; font-weight: 700; margin-bottom: 24px; color: #303133;">🖼️ 素材库</h2>
-                <div class="card">
+                <div class="card page-fade">
                     <div class="filter-bar">
                         <el-input v-model="searchKeyword" placeholder="搜索素材..." style="width: 200px;" clearable @clear="loadAssets" @keyup.enter="loadAssets">
                             <template #prefix><span>🔍</span></template>