Make the listing purge SEO-standard: archive (not delete) + 410 Gone

Per the project archive-not-delete convention, the in-place purge now sets out-of-scope
and duplicate aggregated jobs/shifts to ShiftStatus.Archived instead of hard-deleting:
- The row is retained for analysis and the change is reversible.
- The listing drops out of every public screen and the sitemap (which filter Status == Open).
- Its detail page now returns 410 Gone (the standard permanent-removal signal) so search
  engines deindex it cleanly, instead of leaving the off-topic page live at 200 or hard-404ing.
Dedupe of job reposts archives the older copies the same way. Coordinate backfill now also
skips non-Open rows. Valid listings are untouched, so IDs/URLs stay stable.

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

src/JobsMedical.Web/Pages/Jobs/Details.cshtml.cs

@@ -31,6 +31,9 @@ public class DetailsModel : PageModel
     {
         await LoadAsync(id);
         if (Job is null) return NotFound();
+        // Intentionally removed (admin-archived out-of-scope/duplicate ad): 410 Gone is the standard
+        // signal for permanent removal, so search engines deindex it cleanly (we keep the row for audit).
+        if (Job.Status == ShiftStatus.Archived) return StatusCode(StatusCodes.Status410Gone);
         MapKey = (await _settings.GetAsync()).NeshanMapKey;
         Reported = Request.Query["reported"] == "1";
         await _interest.LogJobAsync(InterestEventType.View, id);