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.cs

@@ -19,6 +19,7 @@ public class IndexModel : PageModel
     // Collections
     public List<Service>     Services     { get; private set; } = new();
     public List<GalleryItem> Gallery      { get; private set; } = new();
+    public int               GalleryTotal { get; private set; } = 0;
     public List<Testimonial> Testimonials { get; private set; } = new();
     public List<BlogPost>    RecentPosts  { get; private set; } = new();
     public List<Faq>         Faqs         { get; private set; } = new();
@@ -39,9 +40,12 @@ public class IndexModel : PageModel
             .OrderBy(s => s.Order)
             .ToListAsync();
 
-        Gallery = await _db.GalleryItems
-            .Where(g => g.IsActive)
+        // Homepage shows only a teaser of 3; full set lives on /gallery
+        var galleryQuery = _db.GalleryItems.Where(g => g.IsActive);
+        GalleryTotal = await galleryQuery.CountAsync();
+        Gallery = await galleryQuery
             .OrderBy(g => g.Order)
+            .Take(3)
             .ToListAsync();
 
         Testimonials = await _db.Testimonials