feat(gallery+editor): dedicated /gallery page, homepage teaser, in-content images

Homepage gallery:
- Show only 3 before/after samples as a teaser (was: all items)
- Add "مشاهده گالری کامل (N نمونه)" CTA when more than 3 exist
- Remove the now-pointless category tabs from the teaser

New /gallery page:
- Full before/after grid with category filter tabs (deduped from data)
- Responsive cards with قبل/بعد labels + captions, empty state
- Added to sitemap.xml (priority 0.8)

Blog content editor:
- New 🖼 تصویر toolbar button inserts an uploaded image at the cursor
  (direct upload, no forced crop) — for richer post bodies
- Responsive img styling on the public post page

Note: the filler-lab-soorat cover not showing is a data issue — that
post has an empty featuredImage in the DB (verified); re-upload + save
fixes it. The upload/save path itself is correct.

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

DrSousan.Api/Pages/Index.cshtml

@@ -529,13 +529,6 @@
       <div class="divider"></div>
       <p class="section-desc">نمونه‌ای از نتایج فوق‌العاده درمان‌های انجام‌شده توسط دکتر آل‌طه.</p>
     </div>
-    <div class="gallery-tabs fade-in">
-      <button class="tab-btn active">همه</button>
-      <button class="tab-btn">بوتاکس</button>
-      <button class="tab-btn">لیزر</button>
-      <button class="tab-btn">مزوتراپی</button>
-      <button class="tab-btn">پاکسازی</button>
-    </div>
     <div class="gallery-grid" id="galleryGrid">
       @if (Model.Gallery.Any())
       {
@@ -592,6 +585,12 @@
           }
       }
     </div>
+    @if (Model.GalleryTotal > 3)
+    {
+        <div class="fade-in" style="text-align:center;margin-top:2.5rem">
+          <a href="/gallery" class="btn-primary">مشاهده گالری کامل (@Model.GalleryTotal نمونه)</a>
+        </div>
+    }
   </div>
 </section>