feat: add referral_code

database/migrations/2026_06_06_000100_add_referral_subscription_granted_at_to_users_table.php

@@ -0,0 +1,27 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('users', function (Blueprint $table) {
+            // When the referral free-month subscription was granted (null = not yet).
+            if (!Schema::hasColumn('users', 'referral_subscription_granted_at')) {
+                $table->timestamp('referral_subscription_granted_at')->nullable()->after('referred_by');
+            }
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('users', function (Blueprint $table) {
+            if (Schema::hasColumn('users', 'referral_subscription_granted_at')) {
+                $table->dropColumn('referral_subscription_granted_at');
+            }
+        });
+    }
+};