fix: create download_keys table on update + element-based key matching

Root cause: the #__mokowaas_download_keys table was only in
install.mysql.sql (fresh installs). Existing sites never got it,
so syncKeysToTable/applyKeysFromTable silently failed.

- Add sql/updates/mysql/02.35.00.sql migration for existing installs
- Register <update><schemas> in component manifest
- Add ensureDownloadKeysTable() as belt-and-suspenders in postflight
- backupDownloadKeys() now saves by element name (stable identifier)
- restoreDownloadKeys() matches by element first, URL second, ID third

Authored-by: Moko Consulting
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

source/script.php

@@ -109,6 +109,9 @@ class Pkg_MokowaasInstallerScript
 		// Clean up stale/duplicate update sites
 		$this->cleanupStaleUpdateSites();
 
+		// Ensure download keys table exists (belt-and-suspenders with schema update)
+		$this->ensureDownloadKeysTable();
+
 		// Restore download keys: first from preflight backup, then from DB table
 		$this->restoreDownloadKeys($this->savedDownloadKeys);
 		$this->reapplyKeysFromDatabase();
@@ -673,6 +676,33 @@ class Pkg_MokowaasInstallerScript
 	 *
 	 * @return  array  Map of update_site_id => extra_query
 	 */
+	/**
+	 * Ensure the download keys table exists.
+	 */
+	private function ensureDownloadKeysTable(): void
+	{
+		try
+		{
+			$db = Factory::getDbo();
+			$db->setQuery("CREATE TABLE IF NOT EXISTS `#__mokowaas_download_keys` (
+				`id` INT UNSIGNED NOT NULL AUTO_INCREMENT,
+				`element` VARCHAR(100) NOT NULL DEFAULT '',
+				`location` VARCHAR(512) NOT NULL DEFAULT '',
+				`dlid` VARCHAR(255) NOT NULL DEFAULT '',
+				`created` DATETIME NOT NULL,
+				`modified` DATETIME NOT NULL,
+				PRIMARY KEY (`id`),
+				UNIQUE KEY `idx_dlkey_element` (`element`),
+				KEY `idx_dlkey_location` (`location`(191))
+			) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4");
+			$db->execute();
+		}
+		catch (\Throwable $e)
+		{
+			// Non-critical
+		}
+	}
+
 	private function backupDownloadKeys(): array
 	{
 		$keys = [];