Fix useless bare-divar.ir links + hide empty homepage shifts section

- Divar listings with no extractable post token were given SourceUrl «https://divar.ir» — a link
  that just opens Divar''s homepage, not the ad. Store null instead, and guard the contact-modal
  fallback to require a real path (so existing bare-domain links stop being offered too).
- Homepage «جدیدترین شیفت‌ها»: only render when there are real open shifts. Almost all aggregated
  ads are ongoing hiring (jobs), not dated shifts, so the section was showing a fabricated shift
  date (the «۱۸ خرداد» on the welcome page). Now it hides when empty.

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

src/JobsMedical.Web/Pages/Index.cshtml

@@ -53,27 +53,25 @@
     </div>
 </section>
 
-<section class="section">
-    <div class="container">
-        <div class="section-head">
-            <h2>جدیدترین شیفت‌ها</h2>
-            <a href="/Shifts">مشاهده همه ←</a>
-        </div>
-        @if (Model.LatestShifts.Count == 0)
-        {
-            <div class="empty-state">فعلاً شیفت بازی ثبت نشده است.</div>
-        }
-        else
-        {
+@* Shifts are rare for aggregated content (most ads are ongoing hiring, not dated shifts) — only
+   show the section when there are real open shifts, so we never display a fabricated/empty date. *@
+@if (Model.LatestShifts.Count > 0)
+{
+    <section class="section">
+        <div class="container">
+            <div class="section-head">
+                <h2>جدیدترین شیفت‌ها</h2>
+                <a href="/Shifts">مشاهده همه ←</a>
+            </div>
             <div class="grid grid-3">
                 @foreach (var s in Model.LatestShifts)
                 {
                     <partial name="_ShiftCard" model="s" />
                 }
             </div>
-        }
-    </div>
-</section>
+        </div>
+    </section>
+}
 
 @if (Model.LatestJobs.Count > 0)
 {