Add migration to fix NULL last_username_change values and enforce default 0

database/migrations/2026_06_08_000001_fix_null_last_username_change_on_users_table.php

@@ -0,0 +1,26 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        DB::table('users')
+            ->whereNull('last_username_change')
+            ->orWhere('last_username_change', 0)
+            ->update(['last_username_change' => 0]);
+
+        Schema::table('users', function (Blueprint $table) {
+            $table->integer('last_username_change')->default(0)->change();
+        });
+    }
+
+    public function down(): void
+    {
+        // Cannot reliably revert default and data changes
+    }
+};