Add documentation for Db Migrator in Single Layer Web Application template

docs/en/solution-templates/single-layer-web-application/db-migrator.md

@@ -0,0 +1,21 @@
+# Single Layer Solution: Db Migrator
+
+````json
+//[doc-nav]
+{
+  "Previous": {
+    "Name": "Web Applications",
+    "Path": "solution-templates/single-layer-web-application/web-applications"
+  },
+  "Next": {
+    "Name": "Built-In Features",
+    "Path": "solution-templates/single-layer-web-application/built-in-features"
+  }
+}
+````
+
+Unlike the Layered solution template, the Single Layer solution template does not include a separate database migrator project. Instead, the main application project handles database migration and seed data operations. The `*.DbMigrator` project is excluded from this template. To manage database migrations and seed data, you can use the `migrate-database.ps1` script in the root directory or run the `dotnet run --migrate-database` command from the main application project directory.
+
+![Single Layer Solution: Db Migrator](images/single-layer-db-migrator.png)
+
+After the migration completes, a message will appear in the console. You can verify the success of the migration by checking the database.