ItemList JSON-LD on Jobs/Shifts list & landing pages

Mark up the result list as a schema.org ItemList (ordered listing URLs) so Google
reads the landing/list pages as a curated collection. Emitted alongside the
breadcrumb JSON-LD when there are results.

Improvement 6 of the backlog (SEO).

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

src/JobsMedical.Web/Services/SeoJsonLd.cs

@@ -145,6 +145,22 @@ public static class SeoJsonLd
         }, Opts));
     }
 
+    /// <summary>ItemList JSON-LD for a results/landing page — an ordered list of the listing URLs,
+    /// so Google understands it as a curated collection. Relative URLs are made absolute.</summary>
+    public static string ItemList(IEnumerable<string> urls, string baseUrl)
+    {
+        var els = urls.Select((u, i) => (object)new Dictionary<string, object?>
+        {
+            ["type"] = "ListItem", ["position"] = i + 1, ["url"] = u.StartsWith("http") ? u : baseUrl + u,
+        }).ToList();
+        return Fix(JsonSerializer.Serialize(new Dictionary<string, object?>
+        {
+            ["@context"] = "https://schema.org",
+            ["@type"] = "ItemList",
+            ["itemListElement"] = els,
+        }, Opts));
+    }
+
     // Nested anonymous objects use "type"/"queryyy" placeholders for @type / query-input;
     // restore the @-prefixed schema.org keys here.
     private static string Fix(string json) => json