fix: filter only active products in getProductByReference

PS soft-deletes products (sets active=0) when deleted from admin,
keeping them in the DB. The previous filter returned those inactive
products, causing pushProduct to take the UPDATE path and silently
re-update a soft-deleted product that remains invisible.

Adding filter[active]=[1] ensures only visible products are matched.
Products deleted in PS are now correctly re-created on next sync.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/integration/prestashop/PrestashopClient.java

@@ -74,6 +74,7 @@ public class PrestashopClient {
                             .queryParam("output_format", "JSON")
                             .queryParam("display", "full")
                             .queryParam("filter[reference]", exactRef)
+                            .queryParam("filter[active]", "[1]")
                             .build())
                     .retrieve()
                     .body(PrestashopProductDto.ListResponse.class);