fix(migration): repair corrupted signature dimension values in app config

postSchemaChange reads the stored signature_width and signature_height
values and replaces any that are non-finite or below
SIGNATURE_DIMENSION_MINIMUM with their respective defaults, emitting a
warning message for each replaced value.

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

Author: vitormattos

lib/Migration/Version17003Date20260404000000.php

@@ -0,0 +1,59 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 LibreCode coop and contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Libresign\Migration;
+
+use Closure;
+use OCA\Libresign\AppInfo\Application;
+use OCA\Libresign\Service\SignatureTextService;
+use OCP\DB\ISchemaWrapper;
+use OCP\IAppConfig;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+class Version17003Date20260404000000 extends SimpleMigrationStep {
+	public function __construct(
+		private IAppConfig $appConfig,
+	) {
+	}
+
+	/**
+	 * @param IOutput $output
+	 * @param Closure(): ISchemaWrapper $schemaClosure
+	 * @param array $options
+	 */
+	#[\Override]
+	public function postSchemaChange(IOutput $output, Closure $schemaClosure, array $options): void {
+		$this->sanitizeDimension(
+			$output,
+			'signature_width',
+			SignatureTextService::DEFAULT_SIGNATURE_WIDTH,
+		);
+		$this->sanitizeDimension(
+			$output,
+			'signature_height',
+			SignatureTextService::DEFAULT_SIGNATURE_HEIGHT,
+		);
+	}
+
+	private function sanitizeDimension(IOutput $output, string $key, float $default): void {
+		$stored = $this->appConfig->getValueFloat(Application::APP_ID, $key, $default);
+		if (is_finite($stored) && $stored >= SignatureTextService::SIGNATURE_DIMENSION_MINIMUM) {
+			return;
+		}
+
+		$this->appConfig->setValueFloat(Application::APP_ID, $key, $default);
+		$output->warning(sprintf(
+			'Restored invalid "%s" value "%s" to default "%s".',
+			$key,
+			(string)$stored,
+			(string)$default,
+		));
+	}
+}