Add unit tests for invoicing period pagination, normalization, and filtering logic

- Implemented `InvoicingPeriodPaginationTest` for testing period pagination modes, normalization of options, search functionality, and visibility filters.
- Added comprehensive tests to validate scenarios such as active period views, exact counts, and customer-card level search.
- Improved cURL timeout settings with `CURLOPT_CONNECTTIMEOUT` and `CURLOPT_TIMEOUT` adjustments.
- Introduced and documented helper classes/methods for local caching, pagination response structure, and customer name retrieval.

services/nginx/app/modules/economic/economic_m.php

@@ -92,7 +92,8 @@ class economic_m
             CURLOPT_RETURNTRANSFER => true,
             CURLOPT_ENCODING => '',
             CURLOPT_MAXREDIRS => 10,
-            CURLOPT_TIMEOUT => 0,
+            CURLOPT_CONNECTTIMEOUT => 3,
+            CURLOPT_TIMEOUT => 10,
             CURLOPT_FOLLOWLOCATION => true,
             CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
             CURLOPT_CUSTOMREQUEST => $method,