feat: add AI stack with Open WebUI, Crawl4AI, and pgvector

Created complete AI infrastructure stack at ai.pivoine.art:

**New Services:**
- **Open WebUI** (ai.pivoine.art)
  - ChatGPT-like interface for AI models
  - Multi-user chat with authentication
  - RAG (Retrieval-Augmented Generation) support
  - Document upload and processing
  - Claude API integration via Anthropic

- **PostgreSQL with pgvector** (dedicated AI database)
  - Vector similarity search for RAG
  - Separate from production databases
  - Stores embeddings and documents

- **Crawl4AI** (internal API service)
  - Web scraping optimized for LLMs
  - Converts websites to clean Markdown
  - Called by n8n workflows
  - No public exposure (internal only)

**Configuration:**
- Added 18 AI environment variables to arty.yml
- Configured email notifications via IONOS SMTP
- OpenAI API compatibility for Claude integration
- Traefik SSL termination and compression

**Backup:**
- Added 3 AI volumes to Restic backup
- Daily backup at 3 AM
- Retention: 7 daily, 4 weekly, 6 monthly, 2 yearly

**Integration:**
- Shares falcon_network with existing services
- Ready for n8n workflow automation
- Mattermost notifications support
- Watchtower auto-updates enabled

Ready for Phase 2: GPU server integration with Ollama, Whisper, and
Stable Diffusion when IONOS A10 server is provisioned.

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

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

restic/config.json

@@ -280,6 +280,26 @@
           "monthly": 3
         }
       }
+    },
+    {
+      "id": "ai-backup",
+      "repo": "hidrive-backup",
+      "paths": [
+        "/volumes/ai_postgres_data",
+        "/volumes/ai_webui_data",
+        "/volumes/ai_crawl4ai_data"
+      ],
+      "schedule": {
+        "cron": "0 3 * * *"
+      },
+      "retention": {
+        "policyTimeBucketed": {
+          "daily": 7,
+          "weekly": 4,
+          "monthly": 6,
+          "yearly": 2
+        }
+      }
     }
   ]
 }