Refactor product relations to use new category_product and channel_product tables

- Updated queries and relationships in various controllers and models to replace `product_has_relations` with `category_product` and `channel_product`.
- Adjusted methods in `ProductFilterer`, `FilterParamsController`, and `FilterController` to reflect the new database structure.
- Modified seeder to insert data into the new `channel_product` table.
- Updated tests to ensure compatibility with the new product relation structure.

tests/Feature/Api/V1/ProductTest.php

@@ -217,7 +217,7 @@ test('can list related products', function () {
     // Then it selects product_ids from those categories.
     // It doesn't explicitly exclude the main product ID in the query shown in tool output?
     // Let's check the controller code again.
-    // It selects `product_has_relations.product_id` where `productable_id` IN (categories of main product).
+    // It selects `category_product.product_id` where `category_id` IN (categories of main product).
     // It does NOT seem to exclude the main product ID in the query.
     // However, `unique()` is used.
     // If the main product is returned, count would be 3. If excluded, 2.