Add how-to guide for restoring 1Password backup from borgmatic (#141)

## Summary
- New how-to guide at `docs/how-to/restore-1password-backup.md` with step-by-step procedure for extracting and decrypting a 1Password `.1pux` export from borgmatic backup
- **End-to-end verified**: extracted from today's borg archive, decrypted age key with openssl, decrypted .1pux with age → valid 31MB zip with vault data
- Cross-links added from: disaster-recovery, 1password, borgmatic, backups policy, and how-to index
- Updated disaster-recovery.md from TBD stub to include a procedures table

## Deployment and Testing
- [x] Verified full extraction + decryption flow against live borgmatic archive
- [x] `docs-check-links` passes — all wiki-links valid
- [ ] Review guide for clarity and completeness

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/141

docs/reference/storage/backups.md

@@ -24,7 +24,7 @@ Daily automated backups from [[indri]] to [[sifaka|Sifaka]] NAS.
 | `~/code/personal/zk` | Zettelkasten notes | Critical |
 | `/opt/homebrew/var/forgejo` | Git repositories | Critical |
 | `~/.config/borgmatic` | Backup config | High |
-| `~/Documents` | Personal documents | High |
+| `~/Documents` | Personal documents (includes [[1password]] encrypted export) | High |
 
 ### Databases
 
@@ -72,3 +72,4 @@ Dashboard: "Borgmatic Backups" in [[grafana]]
 - [[borgmatic]] - Backup system details
 - [[sifaka|Sifaka]] - Backup storage
 - [[postgresql]] - Database backups
+- [[restore-1password-backup]] - Recover 1Password from backup