feat: add Restic backup stack with Backrest UI

Added comprehensive backup solution to The Falcon infrastructure:

- **Restic Stack** (restic.pivoine.art):
  - Backrest web UI for managing restic backups
  - Automated scheduled backups with retention policies
  - Real-time backup status and monitoring
  - Restore capabilities via web interface

- **Backup Configuration**:
  - Target: /mnt/hidrive/users/valknar/Backup
  - Backs up all critical Docker volumes read-only:
    - PostgreSQL, Redis, Directus (uploads/bundle)
    - Awesome, Gotify, Scrapy (data/code)
    - n8n workflows, Filestash state
    - Linkwarden bookmarks/search index
    - Let's Encrypt SSL certificates

- **Infrastructure Updates**:
  - Added RESTIC_* environment variables to arty.yml
  - Updated compose.yaml to include restic stack
  - Updated README.md and CLAUDE.md documentation
  - Configured Traefik routing with SSL

All volumes mounted read-only to backup container for safety.
Backrest data persisted across: data, config, cache, tmp volumes.

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

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

README.md

@@ -52,6 +52,7 @@ The **Falcon** is a state-of-the-art containerized starship, powered by Docker's
 | **N8N** | *Automated workflow command center* | [n8n.pivoine.art](https://n8n.pivoine.art) |
 | **STASH** | *Universal file management portal* | [stash.pivoine.art](https://stash.pivoine.art) |
 | **LINKS** | *Interstellar bookmark archive* | [links.pivoine.art](https://links.pivoine.art) |
+| **RESTIC** | *Automated backup vault system* | [restic.pivoine.art](https://restic.pivoine.art) |
 | **PROXY** | *Shield control dashboard* | [proxy.pivoine.art](https://proxy.pivoine.art) |
 | **VPN** | *Cloaking device network* | [vpn.pivoine.art](https://vpn.pivoine.art) |
 
@@ -74,6 +75,11 @@ The **Falcon** is a state-of-the-art containerized starship, powered by Docker's
 ├─────────────────────────────────────────────────┤
 │  ⚡ REDIS CACHE HYPERDRIVE                     │
 │  └─ Warp-speed data acceleration               │
+├─────────────────────────────────────────────────┤
+│  🔐 BACKREST BACKUP VAULT (Restic)             │
+│  ├─ Automated volume snapshots                 │
+│  ├─ Incremental backup engine                  │
+│  └─ HiDrive remote repository                  │
 └─────────────────────────────────────────────────┘
 ```
 
@@ -172,6 +178,7 @@ THE FALCON (falcon_network)
 │  ├─ n8n Workflows      [n8n.pivoine.art]
 │  ├─ Filestash Files    [stash.pivoine.art]
 │  ├─ Linkwarden Marks   [links.pivoine.art]
+│  ├─ Backrest Backups   [restic.pivoine.art]
 │  └─ WireGuard VPN      [vpn.pivoine.art]
 │
 └─ 💾 STORAGE VOLUMES
@@ -185,6 +192,8 @@ THE FALCON (falcon_network)
    ├─ filestash_data     → File manager state
    ├─ linkwarden_data    → Bookmark archives
    ├─ meili_data         → Search index database
+   ├─ backrest_data      → Backup system state
+   ├─ backrest_config    → Backup configurations
    └─ letsencrypt_data   → Shield certificates
 ```