fix: add DEFAULT 0 to last_username_change column, seeder, fillable, and factory

database/seeders/UpdateLastUsernameChangeSeeder.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Database\Seeders;
+
+use Illuminate\Database\Seeder;
+use Illuminate\Support\Facades\DB;
+
+class UpdateLastUsernameChangeSeeder extends Seeder
+{
+    public function run(): void
+    {
+        DB::table('users')
+            ->whereNull('last_username_change')
+            ->orWhere('last_username_change', 0)
+            ->update(['last_username_change' => 0]);
+    }
+}