M1: key management, backup locations and occ commands

- migration: ngb_targets, ngb_runs, ngb_snapshots
- KeyService: master key stored encrypted with the instance secret
  (unattended backups), passphrase-wrapped copy in every repository and
  in the recovery kit, recorded admin confirmation per key fingerprint
- TargetService: locations built from files_external backends without a
  mount; files_external is loaded through IAppManager::loadApp() and its
  enabled state is left alone; credentials encrypted with ICrypto;
  existing repositories are adopted only if made with this key, and a
  repository cannot be registered twice
- Repository: initWithKey/openWithKey with an encrypted key check
- occ: backup:key:init|kit|confirm, backup:target:backends|add|list|remove

lib/Command/TargetAdd.php

@@ -0,0 +1,73 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\KeyService;
+use OCA\NgBackup\Service\TargetService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+
+class TargetAdd extends Command {
+	public function __construct(
+		private TargetService $targets,
+		private KeyService $keys,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:target:add')
+			->setDescription('Add a backup location (S3, SFTP, WebDAV, ...) via files_external, without mounting it')
+			->addArgument('name', InputArgument::REQUIRED, 'Name of the location')
+			->addArgument('backend', InputArgument::REQUIRED, 'files_external backend id (see backup:target:backends)')
+			->addOption('auth', 'a', InputOption::VALUE_REQUIRED, 'Auth mechanism id (see backup:target:backends)')
+			->addOption('option', 'o', InputOption::VALUE_REQUIRED | InputOption::VALUE_IS_ARRAY, 'Backend/auth option key=value (repeatable)')
+			->addOption('path', 'p', InputOption::VALUE_REQUIRED, 'Folder on the location for this repository', 'ng_backup')
+			->setHelp(<<<'HELP'
+The location is reached with files_external's own connection code, but it is never added as an
+external storage: it does not appear in Files for anyone. Credentials are stored encrypted.
+
+Examples:
+  occ backup:target:add offsite amazons3 -a amazons3::accesskey       -o bucket=backups -o hostname=s3.example.com -o region=eu-central-1       -o use_ssl=true -o use_path_style=true -o key=AKIA... -o secret=... --path=nextcloud
+
+  occ backup:target:add nas sftp -a password::password       -o host=nas.example.lan -o root=/backups -o user=nextcloud -o password=... --path=ng_backup
+HELP);
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		if (!$this->keys->isInitialized()) {
+			$output->writeln('<error>No backup key yet: run occ backup:key:init first.</error>');
+			return 1;
+		}
+		$options = [];
+		foreach ($input->getOption('option') as $pair) {
+			if (!str_contains($pair, '=')) {
+				$output->writeln("<error>Option '$pair' must be key=value</error>");
+				return 1;
+			}
+			[$k, $v] = explode('=', $pair, 2);
+			$options[$k] = match (strtolower($v)) { 'true' => true, 'false' => false, default => $v };
+		}
+		if ($input->getOption('auth') === null) {
+			$output->writeln('<error>--auth is required (see occ backup:target:backends)</error>');
+			return 1;
+		}
+		try {
+			$r = $this->targets->add($input->getArgument('name'), $input->getArgument('backend'), $input->getOption('auth'), $options, (string)$input->getOption('path'));
+		} catch (\Throwable $e) {
+			$output->writeln('<error>' . $e->getMessage() . '</error>');
+			return 1;
+		}
+		$output->writeln(sprintf('Location <info>%s</info> added (id %d), repository %s %s.', $r['target']->getName(), $r['target']->getId(),
+			$r['target']->getRepositoryId(), $r['created'] ? 'created' : 'found and adopted'));
+		return 0;
+	}
+}