fix(blog): align soft delete with deleted_at

db/migrations/V031__AddBlogDeletedAtColumn.sql

@@ -0,0 +1,6 @@
+ALTER TABLE blog_posts
+    ADD COLUMN IF NOT EXISTS deleted_at TIMESTAMPTZ;
+
+CREATE INDEX IF NOT EXISTS idx_blog_posts_deleted_at
+    ON blog_posts (deleted_at)
+    WHERE deleted_at IS NOT NULL;