Feature: Recommendation Service

This commit introduces a RecommendationService that is used when indexing products.

The service is utilizing a recommendation rules interface, so many rules can be created and applied during indexing the products

src/Catalog/Events/ProductDeleted.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Modules\Core\Catalog\Events;
+
+/**
+ * Dispatched whenever a Product is deleted (see CatalogServiceProvider,
+ * which wires this to the model's own deleted() hook — fires for both a
+ * soft delete and a force delete, same as Laravel Scout's own
+ * ModelObserver::deleted() that triggers unsearchable() for the product
+ * itself). Same purpose as Modules\Core\Catalog\Events\ProductSaved: lets
+ * Modules\Core\Catalog\Listeners\ReindexProductsRecommendingProduct find
+ * and re-index every OTHER product that currently embeds this one in its
+ * `recommendations` field, so a deleted product doesn't linger as a dead
+ * reference elsewhere. Carries only the id, not the Product model — by the
+ * time this fires the model may already be gone (force delete), and the
+ * reverse lookup only ever needs the id to filter on.
+ */
+class ProductDeleted
+{
+    public function __construct(
+        public readonly int $productId,
+    ) {}
+}

src/Catalog/Events/ProductSaved.php

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+<?php
+
+namespace Modules\Core\Catalog\Events;
+
+use Lunar\Models\Product;
+
+/**
+ * Dispatched whenever a Product is saved (see CatalogServiceProvider,
+ * which wires this to the model's own saved() hook) — exists specifically
+ * so Modules\Core\Catalog\Listeners\ReindexProductsRecommendingProduct can
+ * find and re-index every OTHER product that currently embeds this one in
+ * its own `recommendations` field (see ProductIndexer). Those products
+ * have no direct database relationship to this one — a recommendation is
+ * computed and stored only inside Meilisearch (Modules\Core\Catalog\
+ * Services\RecommendationService) — so nothing about their own save
+ * lifecycle would otherwise pick up this product's changed name/price/
+ * image.
+ */
+class ProductSaved
+{
+    public function __construct(
+        public readonly Product $product,
+    ) {}
+}