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/TargetRemove.php

@@ -0,0 +1,40 @@
+<?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\TargetService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+class TargetRemove extends Command {
+	public function __construct(
+		private TargetService $targets,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:target:remove')
+			->setDescription('Remove a backup location from NG Backup (the backups on it are kept)')
+			->addArgument('target', InputArgument::REQUIRED, 'Name or id');
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		try {
+			$t = $this->targets->get($input->getArgument('target'));
+		} catch (\Throwable) {
+			$output->writeln('<error>No such location.</error>');
+			return 1;
+		}
+		$this->targets->remove($t);
+		$output->writeln('Removed <info>' . $t->getName() . '</info>. The backups on the location itself were not touched; add it again to use them.');
+		return 0;
+	}
+}