fix(blog): auto-generate slug when admin leaves it empty

Allow optional slug on create/update, generate from title with unique fallback,
so BackOffice can publish posts without manual slug entry.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/CMSMicroservice.Application/Common/BlogSlugHelper.cs

@@ -0,0 +1,85 @@
+using CMSMicroservice.Application.Common.Interfaces;
+using Microsoft.EntityFrameworkCore;
+
+namespace CMSMicroservice.Application.Common;
+
+public static class BlogSlugHelper
+{
+    private const int MaxSlugLength = 200;
+
+    public static string? NormalizeOptional(string? slug)
+    {
+        if (string.IsNullOrWhiteSpace(slug))
+            return null;
+
+        return slug.Trim().ToLowerInvariant();
+    }
+
+    /// <summary>
+    /// Builds a URL slug from title (ASCII letters/digits). Persian-only titles yield empty string.
+    /// </summary>
+    public static string GenerateFromTitle(string title)
+    {
+        if (string.IsNullOrWhiteSpace(title))
+            return string.Empty;
+
+        var sb = new System.Text.StringBuilder();
+        var lastWasHyphen = false;
+
+        foreach (var c in title.Trim().ToLowerInvariant())
+        {
+            if (c is >= 'a' and <= 'z' or >= '0' and <= '9')
+            {
+                sb.Append(c);
+                lastWasHyphen = false;
+            }
+            else if (c is ' ' or '_' or '-')
+            {
+                if (sb.Length > 0 && !lastWasHyphen)
+                {
+                    sb.Append('-');
+                    lastWasHyphen = true;
+                }
+            }
+        }
+
+        var result = sb.ToString().Trim('-');
+        return result.Length > MaxSlugLength ? result[..MaxSlugLength].TrimEnd('-') : result;
+    }
+
+    public static string CreateFallbackSlug() =>
+        $"post-{Guid.NewGuid():N}"[..Math.Min(20, MaxSlugLength)];
+
+    public static string ResolveForCreate(string? requestedSlug, string title)
+    {
+        var normalized = NormalizeOptional(requestedSlug);
+        if (!string.IsNullOrEmpty(normalized))
+            return normalized;
+
+        var fromTitle = GenerateFromTitle(title);
+        return !string.IsNullOrEmpty(fromTitle) ? fromTitle : CreateFallbackSlug();
+    }
+
+    public static async Task<string> EnsureUniquePostSlugAsync(
+        IApplicationDbContext context,
+        string slug,
+        long? excludePostId = null,
+        CancellationToken cancellationToken = default)
+    {
+        var candidate = slug;
+        var suffix = 2;
+
+        while (await context.BlogPosts.AnyAsync(
+            p => p.Slug == candidate && !p.IsDeleted && (excludePostId == null || p.Id != excludePostId.Value),
+            cancellationToken))
+        {
+            var suffixStr = $"-{suffix}";
+            var maxBase = MaxSlugLength - suffixStr.Length;
+            var basePart = slug.Length > maxBase ? slug[..maxBase].TrimEnd('-') : slug;
+            candidate = basePart + suffixStr;
+            suffix++;
+        }
+
+        return candidate;
+    }
+}