feat(backup): full DR bundle export + admin-configurable offsite destinations

Backend-agnostic disaster-recovery backup engine that runs on the current
storage backend (no storage cutover required):

- Full-bundle export: db.dump (pg_dump custom) + every storage blob +
  manifest.json with per-object SHA-256, streamed as a tar. Entry points:
  admin UI download, GET /api/v1/admin/backup/export, scripts/create-full-backup.ts.
- Admin-configurable push destinations (backup_destinations table, migration
  0091): SFTP/SSH, S3-compatible (reuses the minio client), and mounted
  path/NAS behind one transport interface (test/push/prune). Secrets AES-GCM
  at rest; API returns only *IsSet markers.
- Opt-in per-destination AES-256 bundle encryption (scrypt KDF, streamed) +
  scripts/decrypt-backup.ts for restore.
- Wired the previously-dead database-backup cron to runScheduledBackupPush
  (push to enabled destinations, prune to retention, alert super-admins on
  failure).

Tests: 1608 unit/integration pass; tsc + lint clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/decrypt-backup.ts

@@ -0,0 +1,31 @@
+/**
+ * Decrypt an encrypted backup bundle (`*.tar.enc`) produced when a destination
+ * has bundle encryption enabled. Restore step — see
+ * docs/backup-restore-runbook.md.
+ *
+ *   BACKUP_PASSPHRASE='…' pnpm tsx scripts/decrypt-backup.ts <in.tar.enc> <out.tar>
+ *
+ * The passphrase is read from $BACKUP_PASSPHRASE (not argv, to keep it out of
+ * shell history / the process list).
+ */
+import { decryptFileToFile } from '@/lib/services/backup-destinations/bundle-encryption';
+
+async function main(): Promise<void> {
+  const [input, output] = process.argv.slice(2);
+  const passphrase = process.env.BACKUP_PASSPHRASE;
+  if (!input || !output) {
+    throw new Error(
+      'Usage: BACKUP_PASSPHRASE=… pnpm tsx scripts/decrypt-backup.ts <in.tar.enc> <out.tar>',
+    );
+  }
+  if (!passphrase) throw new Error('Set BACKUP_PASSPHRASE in the environment');
+  await decryptFileToFile(input, output, passphrase);
+  process.stdout.write(`Decrypted → ${output}\n`, () => process.exit(0));
+}
+
+main().catch((err) => {
+  process.stderr.write(
+    `Decrypt failed: ${err instanceof Error ? err.message : String(err)}\n`,
+    () => process.exit(1),
+  );
+});