fix(scheduled-tasks): drop leftover failure_count and auto_disabled_at

Instances that ran a since-removed migration from an earlier version of
task auto-disable still have these columns. The current implementation
uses consecutive_failures, failing_since, and disabled_reason instead.
The migration checks that each column exists before dropping it.

database/migrations/2026_11_09_120000_drop_unused_failure_columns_from_scheduled_tasks.php

@@ -0,0 +1,28 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Instances that ran a removed migration of an earlier version of task auto-disable still have these columns.
+     * The current version uses consecutive_failures, failing_since, and disabled_reason.
+     */
+    public function up(): void
+    {
+        foreach (['failure_count', 'auto_disabled_at'] as $column) {
+            if (Schema::hasColumn('scheduled_tasks', $column)) {
+                Schema::table('scheduled_tasks', function (Blueprint $table) use ($column) {
+                    $table->dropColumn($column);
+                });
+            }
+        }
+    }
+
+    public function down(): void
+    {
+        //
+    }
+};