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/Jobs/Details.cshtml

@@ -23,10 +23,14 @@
     if (j.SalaryMin is null && j.SalaryMax is null) salary = "توافقی";
     else if (j.SalaryMin == j.SalaryMax) salary = JalaliDate.Toman(j.SalaryMin) + " ماهانه";
     else salary = $"از {JalaliDate.ToPersianDigits((j.SalaryMin ?? 0).ToString("#,0"))} تا {JalaliDate.Toman(j.SalaryMax)} ماهانه";
+    var crumbs = new List<JobsMedical.Web.Services.Crumb> { new("خانه", "/"), new("استخدام", "/Jobs") };
+    if (j.Role is not null) crumbs.Add(new(j.Role.Name, "/استخدام/" + JobsMedical.Web.Services.SeoSlug.Of(j.Role.Name)));
+    crumbs.Add(new(j.Title, 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 badge-job">@empLabel</span>
             @if (j.Role is not null) { <span class="badge badge-type">@j.Role.Name</span> }
@@ -199,9 +203,10 @@
 @section Head {
     @* Only emit JobPosting structured data for a real named employer — Google for Jobs rejects a
        placeholder/empty hiringOrganization (most aggregated ads have no named center). *@
+    @{ 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>")
     @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.JobPosting(j, bu) + "</script>")
     }
 }