fix: 修复SEO工具页面模板继承错误，改为独立完整HTML页面

- 将seo_tools.html从继承admin/master.html改为独立完整HTML
- 从master.html中移除SEO工具菜单项，避免url_for错误
- 修复本地UndefinedError: 'admin_view' is undefined错误

templates/admin/master.html

@@ -79,12 +79,6 @@
             <div class="nav-section">
                 <div class="nav-section-title">系统</div>
                 <ul class="nav-menu">
-                    <li class="nav-item">
-                        <a href="{{ url_for('seo_tools') }}" class="nav-link">
-                            <span class="material-symbols-outlined nav-icon">search</span>
-                            <span class="nav-text">SEO工具</span>
-                        </a>
-                    </li>
                     <li class="nav-item">
                         <a href="{{ url_for('batch_import') }}" class="nav-link">
                             <span class="material-symbols-outlined nav-icon">upload_file</span>