feat(scheduling): persist and claim scheduled job occurrences

Add database-backed schedule states and deliveries so distributed schedulers publish each occurrence once, queue jobs claim executions atomically, and stale occurrences are cleaned up.

database/migrations/2026_09_18_111936_create_scheduled_job_states_and_deliveries_tables.php

@@ -0,0 +1,49 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::create('scheduled_job_states', function (Blueprint $table) {
+            $table->id();
+            $table->string('uuid')->unique();
+            $table->string('schedule_key')->unique();
+            $table->timestampTz('last_scheduled_for')->nullable();
+            $table->timestamps();
+        });
+
+        Schema::create('scheduled_job_deliveries', function (Blueprint $table) {
+            $table->id();
+            $table->string('uuid')->unique();
+            $table->string('schedule_key');
+            $table->timestampTz('scheduled_for');
+            $table->string('job_type');
+            $table->unsignedBigInteger('resource_id');
+            $table->json('payload')->nullable();
+            $table->string('status')->default('pending');
+            $table->string('claim_token')->nullable();
+            $table->timestampTz('enqueued_at')->nullable();
+            $table->timestampTz('started_at')->nullable();
+            $table->timestamps();
+
+            $table->unique(['schedule_key', 'scheduled_for']);
+            $table->index(['status', 'created_at']);
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('scheduled_job_deliveries');
+        Schema::dropIfExists('scheduled_job_states');
+    }
+};