Fix MCP occurrence apostrophe escaping

scripts/tests/market_management_sanitizer_test.php

@@ -0,0 +1,28 @@
+<?php
+declare(strict_types=1);
+
+require_once __DIR__ . '/../../modules/market_management/service.php';
+
+function fail_test(string $message): void
+{
+    fwrite(STDERR, $message . PHP_EOL);
+    exit(1);
+}
+
+function assert_test(bool $condition, string $message): void
+{
+    if (!$condition) {
+        fail_test($message);
+    }
+}
+
+$plainText = "Test 'A' & <B> \"C\"";
+$sanitized = market_management_sanitize_multiline_html($plainText);
+assert_test($sanitized === "Test 'A' &amp; &lt;B&gt; \"C\"", 'Plain text must preserve quotes and escape markup characters once');
+
+$link = '<a href="https://erpnaurua.imhochrain.ch/files.php?path=Marktmanagement%2Fvertrag.pdf">Vertrag</a>';
+$sanitizedLink = market_management_sanitize_multiline_html($link);
+assert_test(str_contains($sanitizedLink, 'class="sg-hyperlink"'), 'Allowed links must remain links');
+assert_test(str_contains($sanitizedLink, 'href="https://erpnaurua.imhochrain.ch/files.php?path=Marktmanagement%2Fvertrag.pdf"'), 'Link href must remain valid');
+
+fwrite(STDOUT, "market_management_sanitizer_test: OK\n");