feat(seo): complete OG/Twitter/structured-data coverage + clean encoding

Blog list (/blog): add robots, full Open Graph + Twitter, Blog +
BreadcrumbList JSON-LD, per-page self-canonical, and rel=prev/next for
paginated pages.

Blog post: add robots, og:site_name, article:published_time /
modified_time / author / section, twitter:image, og:image:alt, and a
BreadcrumbList JSON-LD (Home → Blog → Category → Post).

Gallery (/gallery): add robots, full OG + Twitter (with first image as
og:image), ImageGallery + BreadcrumbList JSON-LD.

Encoding: register HtmlEncoder.Create(UnicodeRanges.All) so Persian text
in meta tags and JSON-LD renders literally instead of &#xXXXX; entities
(smaller, cleaner output; friendlier to SEO validators).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

DrSousan.Api/Pages/Blog/Index.cshtml

@@ -1,10 +1,58 @@
 @page "/blog"
 @model DrSousan.Api.Pages.Blog.BlogIndexModel
+@{
+    var blogBase   = Environment.GetEnvironmentVariable("SITE_BASE_URL")?.TrimEnd('/') ?? (Request.Scheme + "://" + Request.Host);
+    var catQs      = string.IsNullOrEmpty(Model.ActiveCat) ? "" : "&category=" + Model.ActiveCat;
+    string PageUrl(int p) => p <= 1
+        ? blogBase + "/blog" + (string.IsNullOrEmpty(Model.ActiveCat) ? "" : "?category=" + Model.ActiveCat)
+        : blogBase + "/blog?pg=" + p + catQs;
+    var blogDesc   = "مقالات تخصصی دکتر سوسن آل‌طه درباره زیبایی پوست، بوتاکس، فیلر، لیزر و مراقبت از پوست.";
+}
 
 @section Head {
     <title>@ViewData["Title"]</title>
-    <meta name="description" content="مقالات تخصصی دکتر سوسن آل‌طه درباره زیبایی پوست، بوتاکس، فیلر، لیزر و مراقبت از پوست." />
-    <link rel="canonical" href="@((Environment.GetEnvironmentVariable("SITE_BASE_URL")?.TrimEnd('/') ?? (Request.Scheme + "://" + Request.Host)) + "/blog")" />
+    <meta name="description" content="@blogDesc" />
+    <meta name="robots" content="index, follow, max-image-preview:large, max-snippet:-1" />
+    <meta name="author" content="@ViewData["SiteName"]" />
+    <meta name="theme-color" content="#B8955A" />
+    <link rel="canonical" href="@PageUrl(Model.CurrentPage)" />
+    @if (Model.CurrentPage > 1) { <link rel="prev" href="@PageUrl(Model.CurrentPage - 1)" /> }
+    @if (Model.CurrentPage < Model.TotalPages) { <link rel="next" href="@PageUrl(Model.CurrentPage + 1)" /> }
+
+    <!-- Open Graph -->
+    <meta property="og:type"        content="website" />
+    <meta property="og:site_name"   content="@ViewData["SiteName"]" />
+    <meta property="og:title"       content="@ViewData["Title"]" />
+    <meta property="og:description" content="@blogDesc" />
+    <meta property="og:url"         content="@PageUrl(Model.CurrentPage)" />
+    <meta property="og:locale"      content="fa_IR" />
+    <!-- Twitter -->
+    <meta name="twitter:card"        content="summary" />
+    <meta name="twitter:title"       content="@ViewData["Title"]" />
+    <meta name="twitter:description" content="@blogDesc" />
+
+    <!-- Structured data: Blog + breadcrumb -->
+    <script type="application/ld+json">
+    {
+      "@@context": "https://schema.org",
+      "@@type": "Blog",
+      "name": "@ViewData["Title"]",
+      "description": "@blogDesc",
+      "url": "@(blogBase)/blog",
+      "inLanguage": "fa-IR",
+      "publisher": { "@@type": "Organization", "name": "@ViewData["SiteName"]", "url": "@blogBase" }
+    }
+    </script>
+    <script type="application/ld+json">
+    {
+      "@@context": "https://schema.org",
+      "@@type": "BreadcrumbList",
+      "itemListElement": [
+        { "@@type": "ListItem", "position": 1, "name": "خانه", "item": "@blogBase/" },
+        { "@@type": "ListItem", "position": 2, "name": "وبلاگ", "item": "@blogBase/blog" }
+      ]
+    }
+    </script>
     <style>
       /* ─── Blog Hero ─────────────────────────────────────────────── */
       .blog-hero{background:linear-gradient(135deg,var(--gold-pale) 0%,#EDE0CA 100%);padding:6rem 2rem 3rem;text-align:center}