refactor: Use PSR-4 version of horde/nls

.gitignore

@@ -52,3 +52,9 @@ vendor/
 /phpstan.neon
 # PHPStan cache directory
 /.phpstan.cache/
+
+# Added by horde-components QC --fix-qc-issues
+# Horde installer plugin runtime data
+/var/
+# Horde installer plugin web-accessible directory
+/web/

lib/Horde/Mime/Part.php

@@ -1318,7 +1318,7 @@ public function getSize($approx = false)
             return 0;
         }
 
-        $localeinfo = Horde_Nls::getLocaleInfo();
+        $localeinfo = (new Horde\Nls\Nls())->getLocaleInfo();
 
         // TODO: Workaround broken number_format() prior to PHP 5.4.0.
         return str_replace(

test/unit/PartGetSizeTest.php

@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\Mime\Test;
+
+use Horde_Mime_Part;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Tests the public getSize() contract of Horde_Mime_Part.
+ *
+ * getSize() internally uses Horde_Nls::getLocaleInfo() to format numbers
+ * with locale-specific decimal/thousands separators.
+ * @coversNothing
+ */
+class PartGetSizeTest extends TestCase
+{
+    public function testGetSizeReturnsFormattedKilobytes(): void
+    {
+        $part = new Horde_Mime_Part();
+        $part->setBytes(10240);
+
+        $result = $part->getSize();
+
+        $this->assertIsString($result);
+        $this->assertStringContainsString('10', $result);
+    }
+
+    public function testGetSizeReturnsZeroForEmptyPart(): void
+    {
+        $part = new Horde_Mime_Part();
+
+        $result = $part->getSize();
+
+        $this->assertEquals(0, $result);
+    }
+
+    public function testGetSizeWithLargeValue(): void
+    {
+        $part = new Horde_Mime_Part();
+        $part->setBytes(1048576);
+
+        $result = $part->getSize();
+
+        $this->assertIsString($result);
+        $this->assertStringContainsString('1', $result);
+    }
+
+    public function testGetSizeWithApprox(): void
+    {
+        $part = new Horde_Mime_Part();
+        $part->setBytes(5120);
+
+        $result = $part->getSize(true);
+
+        $this->assertIsString($result);
+        $this->assertStringContainsString('5', $result);
+    }
+}