Breadcrumbs: visible trail + BreadcrumbList JSON-LD

Add SeoJsonLd.Breadcrumb + Crumb record + _Breadcrumbs partial, and wire a trail
into the Jobs/Shifts list (landing) and detail pages: خانه › استخدام/شیفت › {نقش}
› {شهر|عنوان}. The role crumb links to the role landing page (more internal
links), and Google can show the breadcrumb path in results. Detail pages emit it
alongside the existing JobPosting JSON-LD.

Improvement 5 of the backlog (SEO).

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

src/JobsMedical.Web/Pages/Shifts/Details.cshtml

@@ -21,10 +21,14 @@
         ShiftType.Night => ("badge-night", "شیفت شب"),
         _ => ("badge-oncall", "آنکال"),
     };
+    var crumbs = new List<JobsMedical.Web.Services.Crumb> { new("خانه", "/"), new("شیفت‌ها", "/Shifts") };
+    if (s.Role is not null) crumbs.Add(new(s.Role.Name, "/شیفت/" + JobsMedical.Web.Services.SeoSlug.Of(s.Role.Name)));
+    crumbs.Add(new(JobsMedical.Web.Services.SeoJsonLd.HasRealEmployer(f) ? f.Name : "جزئیات شیفت", null));
 }
 
 <div class="page-head">
     <div class="container">
+        <partial name="_Breadcrumbs" model="crumbs" />
         <div class="row" style="display:flex; gap:10px; align-items:center;">
             <span class="badge @badgeClass">@typeLabel</span>
             @if (f.IsVerified)
@@ -216,10 +220,11 @@
 }
 
 @section Head {
+    @{ var bu = $"{ViewContext.HttpContext.Request.Scheme}://{ViewContext.HttpContext.Request.Host}"; }
+    @Html.Raw("<script type=\"application/ld+json\">" + JobsMedical.Web.Services.SeoJsonLd.Breadcrumb(crumbs, bu) + "</script>")
     @* Only for a real named employer — Google for Jobs rejects a placeholder hiringOrganization. *@
     @if (JobsMedical.Web.Services.SeoJsonLd.HasRealEmployer(f))
     {
-        var bu = $"{ViewContext.HttpContext.Request.Scheme}://{ViewContext.HttpContext.Request.Host}";
         @Html.Raw("<script type=\"application/ld+json\">" + JobsMedical.Web.Services.SeoJsonLd.ShiftPosting(s, bu) + "</script>")
     }
 }