✨ Optimize post categories, tags usage counting

DysonNetwork.Sphere/Post/Post.cs

@@ -97,6 +97,8 @@ public class PostTag : ModelBase
     [MaxLength(128)] public string Slug { get; set; } = null!;
     [MaxLength(256)] public string? Name { get; set; }
     [JsonIgnore] public ICollection<Post> Posts { get; set; } = new List<Post>();
+    
+    [NotMapped] public int? Usage { get; set; }
 }
 
 public class PostCategory : ModelBase
@@ -105,6 +107,8 @@ public class PostCategory : ModelBase
     [MaxLength(128)] public string Slug { get; set; } = null!;
     [MaxLength(256)] public string? Name { get; set; }
     [JsonIgnore] public ICollection<Post> Posts { get; set; } = new List<Post>();
+    
+    [NotMapped] public int? Usage { get; set; }
 }
 
 public class PostCollection : ModelBase

DysonNetwork.Sphere/Post/PostCategoryController.cs

@@ -33,10 +33,27 @@ public class PostCategoryController(AppDatabase db) : ControllerBase
 
         var totalCount = await categoriesQuery.CountAsync();
         Response.Headers.Append("X-Total", totalCount.ToString());
+        
+        // Get categories with their post counts in a single query
         var categories = await categoriesQuery
             .Skip(offset)
             .Take(take)
+            .Select(c => new 
+            {
+                Category = c,
+                PostCount = c.Posts.Count
+            })
             .ToListAsync();
+
+        // Project results back to the original type and set the Usage property
+        var result = categories.Select(x => 
+        {
+            x.Category.Usage = x.PostCount;
+            return x.Category;
+        }).ToList();
+
+        return Ok(result);
+
         return Ok(categories);
     }
 
@@ -66,12 +83,26 @@ public class PostCategoryController(AppDatabase db) : ControllerBase
 
         var totalCount = await tagsQuery.CountAsync();
         Response.Headers.Append("X-Total", totalCount.ToString());
+        
+        // Get tags with their post counts in a single query
         var tags = await tagsQuery
             .Skip(offset)
             .Take(take)
+            .Select(t => new 
+            {
+                Tag = t,
+                PostCount = t.Posts.Count
+            })
             .ToListAsync();
 
-        return Ok(tags);
+        // Project results back to the original type and set the Usage property
+        var result = tags.Select(x => 
+        {
+            x.Tag.Usage = x.PostCount;
+            return x.Tag;
+        }).ToList();
+
+        return Ok(result);
     }
 
     [HttpGet("categories/{slug}")]