Initial commit: NAS backup, NFS mount docs, NVMe fix docs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

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+# System
+
+Scripts and documentation for system administration tasks.
+
+## NAS Backup
+
+`nas-backup.sh` — rsyncs `/data/backup/` (gitea + postgres) to the NFS-mounted NAS at `/mnt/nas/backup/` every 15 minutes.
+
+- **Timer**: `~/.config/systemd/user/nas-backup.timer`
+- **Service**: `~/.config/systemd/user/nas-backup.service`
+- **Sudoers**: `/etc/sudoers.d/nas-backup` (passwordless rsync)
+
+```bash
+# Check status
+systemctl --user status nas-backup.timer
+systemctl --user list-timers nas-backup.timer
+
+# Run manually
+systemctl --user start nas-backup.service
+
+# View logs
+journalctl --user -u nas-backup.service
+```
+
+## NFS NAS Mount
+
+`nfs-nas-mount.md` — NAS connection details and mount configuration for `nas.local.pmagnus.dk:/omarchy` at `/mnt/nas`.
+
+## NVMe Freeze Fix
+
+`nvme-fix-plan.md` — Fix for Kingston SNV2S2000G freezes caused by NVMe deep power state transitions. Applied via `nvme_core.default_ps_max_latency_us=5000` kernel parameter.