Phase 2: Add Reference section with 24 technical reference cards (#88)

## Summary
- Create `docs/reference/` section with 24 technical reference cards
- Services (16): alloy, argocd, borgmatic, 1password, forgejo, grafana, jellyfin, kiwix, loki, miniflux, navidrome, postgresql, prometheus, teslamate, transmission, zot
- Infrastructure (3): hosts, tailscale, routing
- Kubernetes (2): cluster, apps
- Storage (2): sifaka, backups
- Update README to mark Phase 2 as complete
- Add towncrier changelog fragment

## Deployment and Testing
- [ ] Build docs locally to verify wiki-links resolve
- [ ] Deploy via ArgoCD and verify at docs.ops.eblu.me/reference/

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/88

docs/reference/services/borgmatic.md

@@ -0,0 +1,60 @@
+---
+title: Borgmatic
+tags:
+  - service
+  - backup
+---
+
+# Borgmatic
+
+Daily backup system using Borg backup, running on indri.
+
+## Quick Reference
+
+| Property | Value |
+|----------|-------|
+| **Install** | mise (pipx) |
+| **Config** | `~/.config/borgmatic/config.yaml` |
+| **Schedule** | Daily at 2:00 AM |
+| **Repository** | `/Volumes/backups/borg/` on [[storage/sifaka|Sifaka]] |
+
+## What Gets Backed Up
+
+**Directories:**
+- `~/code/personal/zk` - Zettelkasten
+- `/opt/homebrew/var/forgejo` - Git forge data
+- `~/.config/borgmatic` - Borgmatic config
+- `~/Documents` - Personal documents
+- `~/Pictures` - Photos
+
+**Databases:**
+- `miniflux` on [[postgresql|PostgreSQL]]
+- `teslamate` on [[postgresql|PostgreSQL]]
+
+**Not backed up (by design):**
+- ZIM archives (re-downloadable)
+- Prometheus metrics (ephemeral)
+- Loki logs (ephemeral)
+
+## Retention Policy
+
+| Period | Count |
+|--------|-------|
+| Daily | 7 |
+| Monthly | 12 |
+| Yearly | 1000 |
+
+## Monitoring
+
+Metrics exposed via textfile collector to [[prometheus|Prometheus]]:
+- `borgmatic_up` - Repository accessibility
+- `borgmatic_last_archive_timestamp` - Last backup time
+- `borgmatic_repo_deduplicated_size_bytes` - Disk usage
+
+Dashboard: "Borgmatic Backups" in [[grafana|Grafana]]
+
+## Related
+
+- [[storage/backups|Backups]] - Full backup policy
+- [[storage/sifaka|Sifaka]] - Backup target
+- [[postgresql|PostgreSQL]] - Database backups