refactor(ai): remove crawl4ai service, add backrest config to repo

- Remove crawl4ai service from ai/compose.yaml (will use local MCP instead)
- Remove crawl4ai backup volume from core/compose.yaml
- Add core/backrest/config.json (infrastructure as code)
- Change backrest from volume to bind-mounted config
- Update CLAUDE.md and README.md documentation

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

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

README.md

@@ -406,11 +406,10 @@ THE FALCON (falcon_network)
 │  ├─ vaultwarden        [vault.pivoine.art] → Password Manager
 │  └─ tandoor            [tandoor.pivoine.art] → Recipe Manager
 │
-├─ 🤖 AI STACK (5 services)
+├─ 🤖 AI STACK (4 services)
 │  ├─ ai_postgres        [Internal] → pgvector Database
 │  ├─ webui              [ai.pivoine.art] → Open WebUI (Claude)
 │  ├─ litellm            [llm.ai.pivoine.art] → API Proxy
-│  ├─ crawl4ai           [Internal:11235] → Web Scraper
 │  └─ facefusion         [facefusion.ai.pivoine.art] → Face AI
 │
 ├─ 🛡️ NET STACK (4 services)
@@ -435,7 +434,7 @@ THE FALCON (falcon_network)
    ├─ Core: postgres_data, redis_data, backrest_*
    ├─ Sexy: directus_uploads, directus_bundle
    ├─ Util: pairdrop_*, joplin_data, linkwarden_*, mattermost_*, vaultwarden_data, tandoor_*
-   ├─ AI: ai_postgres_data, ai_webui_data, ai_crawl4ai_data, facefusion_*
+   ├─ AI: ai_postgres_data, ai_webui_data, facefusion_*
    ├─ Net: letsencrypt_data, netdata_*
    ├─ Media: jelly_config, jelly_cache, filestash_data
    └─ Dev: gitea_*, coolify_data, n8n_data, asciinema_data