fix(security): block ORDER BY SQL injection via orderByField (GHSA-cp8p) (#663)

The orderByField/orderBy query params were passed straight into Eloquent's
orderBy() in every model's scopeWhereOrder (and Invoice::scopeApplyFilters),
allowing arbitrary SQL in the ORDER BY clause (boolean-based blind injection).

Adds App\Support\SafeOrderBy::apply() which only accepts a plain, optionally
table-qualified column identifier as the sort target (rejecting expressions,
sub-selects, etc.) and clamps the direction to asc/desc. Routed all 10 model
sort sinks through it. Table-qualified columns stay valid, so joined/aliased
sorts (e.g. estimates by customers.name) are unaffected.

Adds unit tests covering injection rejection, plain + aliased columns, and
direction clamping.

app/Models/RecurringInvoice.php

@@ -5,6 +5,7 @@ namespace App\Models;
 use App\Facades\Hashids;
 use App\Http\Requests\RecurringInvoiceRequest;
 use App\Services\SerialNumberFormatter;
+use App\Support\SafeOrderBy;
 use App\Traits\HasCustomFieldsTrait;
 use Carbon\Carbon;
 use Cron;
@@ -132,7 +133,7 @@ class RecurringInvoice extends Model
 
     public function scopeWhereOrder($query, $orderByField, $orderBy)
     {
-        $query->orderBy($orderByField, $orderBy);
+        return SafeOrderBy::apply($query, $orderByField, $orderBy);
     }
 
     public function scopeWhereStatus($query, $status)