Site-wide rich search with keyword highlighting + header search box

- /Search: searches shifts, hiring openings, and applicants together via
  Postgres ILIKE (every term must match across role/city/facility/title/
  description/tags/person). Results grouped per type.
- Keyword highlighting (<mark>) extended to shift & job cards (was talent-only),
  so matches stand out everywhere.
- Persistent header search box (.nav-search) → /Search; big hero box on the
  page itself.

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

src/JobsMedical.Web/Pages/Shared/_ShiftCard.cshtml

@@ -7,16 +7,17 @@
         ShiftType.Night   => ("badge-night", "شب"),
         _                 => ("badge-oncall", "آنکال"),
     };
+    var q = ViewData["q"] as string;
 }
 <a class="card card-pad shift-card" asp-page="/Shifts/Details" asp-route-id="@Model.Id">
     <div class="row" style="justify-content: space-between;">
-        <span class="facility">@Model.Facility?.Name</span>
+        <span class="facility">@JobsMedical.Web.Services.SearchHighlight.Mark(Model.Facility?.Name, q)</span>
         <span class="badge @badgeClass">@typeLabel</span>
     </div>
     <div class="row">
         @if (Model.Role is not null)
         {
-            <span class="badge badge-type">@Model.Role.Name</span>
+            <span class="badge badge-type">@JobsMedical.Web.Services.SearchHighlight.Mark(Model.Role.Name, q)</span>
         }
         @if (Model.GenderRequirement != Gender.Any)
         {