feat(accounting): add Shayegan as fixed boursecu provider

Wire outbound Invoice/Document sync after confirmed ops, store sync status with timeout lock, and keep SQL credentials out of frontend responses.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/Unit/ShayeganClientErrorMessageTest.php

@@ -0,0 +1,57 @@
+<?php
+
+namespace Tests\Unit;
+
+use App\Services\ShayeganClient;
+use PHPUnit\Framework\TestCase;
+use ReflectionMethod;
+
+class ShayeganClientErrorMessageTest extends TestCase
+{
+    public function test_extract_error_message_from_top_level(): void
+    {
+        $client = $this->clientWithoutConstruct();
+        $method = new ReflectionMethod(ShayeganClient::class, 'extractErrorMessage');
+        $method->setAccessible(true);
+
+        $msg = $method->invoke($client, [
+            'ErrorMessage' => 'missing account',
+            'Result' => [['ErrorMessage' => '', 'Number' => '1']],
+        ]);
+
+        $this->assertSame('missing account', $msg);
+    }
+
+    public function test_extract_error_message_from_result_row(): void
+    {
+        $client = $this->clientWithoutConstruct();
+        $method = new ReflectionMethod(ShayeganClient::class, 'extractErrorMessage');
+        $method->setAccessible(true);
+
+        $msg = $method->invoke($client, [
+            'ErrorMessage' => '',
+            'Result' => [['ErrorMessage' => 'row failed', 'Number' => null]],
+        ]);
+
+        $this->assertSame('row failed', $msg);
+    }
+
+    public function test_empty_error_message_is_success_signal(): void
+    {
+        $client = $this->clientWithoutConstruct();
+        $method = new ReflectionMethod(ShayeganClient::class, 'extractErrorMessage');
+        $method->setAccessible(true);
+
+        $msg = $method->invoke($client, [
+            'ErrorMessage' => '',
+            'Result' => [['ErrorMessage' => '', 'Number' => '12', 'GuId' => 'abc']],
+        ]);
+
+        $this->assertSame('', $msg);
+    }
+
+    private function clientWithoutConstruct(): ShayeganClient
+    {
+        return (new \ReflectionClass(ShayeganClient::class))->newInstanceWithoutConstructor();
+    }
+}