Add: Nextcloud Backblaze B2 backup solution - automated daily backups

- Complete backup script for native Nextcloud (MySQL + files)
- Systemd service and timer for daily automated backups at 2 AM
- Backblaze B2 integration with secure credential storage
- Incremental backup support with 30-day retention
- zstd compression for 40-70% storage reduction
- Comprehensive documentation and deployment guides
- Successfully tested with first backup: 203MB DB + 1.3GB files
- Cost-optimized: ~/bin/bash.01-0.02/month for 1.5GB data

Deployment Details:
- Installed B2 CLI via pipx
- Created backup directories at /opt/nextcloud-backup/
- Configured systemd timer for daily execution at 2 AM
- First backup verified in B2 bucket: jg-nextcloud
- Automated scheduling enabled and tested

Documentation includes:
- Deployment report with complete setup details
- Quick start guide for future deployments
- Comprehensive technical reference
- Troubleshooting procedures
- File manifest and index

nextcloud-backup.timer

@@ -0,0 +1,21 @@
+[Unit]
+Description=Daily Nextcloud to Backblaze B2 Backup Timer
+Documentation=https://backblaze.com/b2/docs/
+Requires=nextcloud-backup.service
+
+[Timer]
+# Run daily at 2 AM (adjust time zone as needed)
+OnCalendar=daily
+OnCalendar=*-*-* 02:00:00
+
+# Also run on boot if we're past the scheduled time
+Persistent=true
+
+# Randomize start time by up to 15 minutes to avoid thundering herd
+RandomizedDelaySec=900
+
+# If the system is shut down during backup, continue on next startup
+AccuracySec=1min
+
+[Install]
+WantedBy=timers.target