Add cron container for daily backups and content export

- Add cron service to docker-compose with backup (3 AM) and export (4 AM) schedules
- Remove redundant content/articles/ and content/curriculum/ (now in Outline, exported to content/wiki/)
- Fix env var mismatch: support both OUTLINE_API_KEY and OUTLINE_API_TOKEN
- Drop updatedAt from export frontmatter to reduce noisy commits
- Add backups/ to gitignore

scripts/export-content.js

@@ -153,7 +153,6 @@ async function main() {
       path: docPath,
       parentDocument: parentTitle,
       outlineId: doc.id,
-      updatedAt: doc.updatedAt,
       createdBy: doc.createdBy?.email || doc.createdBy?.name || null,
     };