fix: standardize billing order status values and apply full-day expiry grace rule

- home_handling_functions.php: display expiration as Y-m-d only (not Y-m-d H:i);
  apply full-day grace by comparing date-only (midnight) in PHP so a server
  expiring on today's date remains Active the entire day
- cron-shop.php Step B & C: change server_expiration_date comparisons from
  < DATE_SUB(NOW(), ...) to DATE(server_expiration_date) < DATE_SUB(CURDATE(), ...)
  ensuring the full expiration day is honoured
- user_games/check_expire.php: change all three expiration queries from
  <= time() to < strtotime(date('Y-m-d')) (today-midnight) for full-day grace
- billing/test_integration.php: replace status='paid' (old order status) with
  status IN ('Active','paid') for backward compat during migration
- user_games/billing_integration.php: clarify comment that billing_invoices.status
  uses the payment lifecycle ('paid'/'unpaid'/'due'), separate from billing_orders.status
- Add modules/billing/sql/normalize_billing_order_status.sql migration script
  to convert installed->Active, paid->Active, suspended->Expired in existing rows
- Update CHANGELOG.md

Agent-Logs-Url: https://github.com/GameServerPanel/GSP/sessions/439845e0-926e-4b49-9cd0-810457b73c12

Co-authored-by: iaretechnician <2749183+iaretechnician@users.noreply.github.com>

modules/user_games/billing_integration.php

@@ -4,8 +4,8 @@
  *
  * Shared helper for recording admin-created game servers in the billing tables,
  * so they are treated identically to FREE website orders:
- *   billing_invoices (status='paid', amount=0)
- *   billing_orders   (status='Active', price=0)
+ *   billing_invoices (status='paid', amount=0)   — invoice payment status (paid/unpaid/due)
+ *   billing_orders   (status='Active', price=0)  — order lifecycle status (Active/Invoiced/Expired)
  *
  * This does NOT re-provision the server — the caller (add_home.php) already
  * created the server via the panel DB layer. We only write the billing ledger
@@ -80,7 +80,11 @@ if (!function_exists('admin_register_server_in_billing')) {
         $ftp_flag  = $ftp ? 'enabled' : 'disabled';
 
         // ------------------------------------------------------------------ //
-        // 3. Insert billing_invoice (amount=0, already "paid").              //
+        // 3. Insert billing_invoice (amount=0, payment_status='paid').       //
+        //    Note: billing_invoices.status is the invoice payment lifecycle  //
+        //    ('paid'/'unpaid'/'due') — distinct from billing_orders.status   //
+        //    which uses the three-value order lifecycle (Active/Invoiced/    //
+        //    Expired).                                                        //
         // ------------------------------------------------------------------ //
         $invoice_fields = array(
             'order_id'                 => 0,