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

cron/entrypoint.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Install node dependencies for export script
+cd /app
+if [ -f scripts/package.json ]; then
+  cd scripts && npm install --production && cd ..
+fi
+
+# Configure git for automated commits
+git config --global --add safe.directory /app
+git config --global user.email "wiki-bot@ghostguild.org"
+git config --global user.name "Wiki Bot"
+
+# Add git remote host to known_hosts so SSH doesn't prompt
+mkdir -p /root/.ssh_tmp
+cp /root/.ssh/* /root/.ssh_tmp/ 2>/dev/null || true
+ssh-keyscan -t ed25519,rsa git.ghostguild.org >> /root/.ssh_tmp/known_hosts 2>/dev/null
+export GIT_SSH_COMMAND="ssh -o UserKnownHostsFile=/root/.ssh_tmp/known_hosts -i /root/.ssh/id_ed25519"
+
+echo "Cron jobs loaded:"
+crontab -l
+echo "Starting crond..."
+
+exec "$@"