fix: preserve insertion order when signingOrder values are equal

When multiple signers have the same signingOrder value, they should
maintain their insertion order (defined by signRequestId) rather than
being sorted alphabetically by displayName.

This change ensures that when signingOrder is equal, signers are
sorted by signRequestId (which is auto-incrementing) instead of
displayName, preserving the order in which they were originally added.

Fixes Behat integration test failures where tests expected signers
to appear in insertion order.

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

lib/Service/FileService.php

@@ -478,7 +478,7 @@ private function loadLibreSignSigners(): void {
 				return $orderA <=> $orderB;
 			}
 
-			return strcasecmp($a['displayName'], $b['displayName']);
+			return ($a['signRequestId'] ?? 0) <=> ($b['signRequestId'] ?? 0);
 		});
 
 		$this->signersLibreSignLoaded = true;
@@ -910,7 +910,7 @@ private function associateAllAndFormat(IUser $user, array $files, array $signers
 						return $orderA <=> $orderB;
 					}
 
-					return strcasecmp($a['displayName'], $b['displayName']);
+					return ($a['signRequestId'] ?? 0) <=> ($b['signRequestId'] ?? 0);
 				});
 
 				$files[$key]['statusText'] = $this->fileMapper->getTextOfStatus((int)$files[$key]['status']);