feat: restore sablog browse modes and clean imported HTML

Keep the public site readable after import (nbsp, highlighter, wrapping code, compact pager) and finish the admin extras already in this tree: sticky levels, preview, page cache, and live llms.txt.

Co-authored-by: Cursor <cursoragent@cursor.com>

resources/views/partials/view-mode-switcher.blade.php

@@ -0,0 +1,9 @@
+@php
+    $viewMode = $homeViewMode ?? \App\Blog\Support\HomeViewMode::LIST;
+@endphp
+<div class="view-mode-switcher">
+    浏览模式:
+    <a href="{{ \App\Blog\Support\HomeViewMode::url(\App\Blog\Support\HomeViewMode::FULL) }}" class="{{ $viewMode === \App\Blog\Support\HomeViewMode::FULL ? 'active' : '' }}">标准</a>
+    <span>|</span>
+    <a href="{{ \App\Blog\Support\HomeViewMode::url(\App\Blog\Support\HomeViewMode::LIST) }}" class="{{ $viewMode === \App\Blog\Support\HomeViewMode::LIST ? 'active' : '' }}">列表</a>
+</div>