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>

CLAUDE.md

@@ -451,12 +451,6 @@ AI infrastructure with Open WebUI, Crawl4AI, and dedicated PostgreSQL with pgvec
   - User signup enabled
   - Data persisted in `ai_webui_data` volume
 
-- **crawl4ai**: Crawl4AI web scraping service (internal API, no public access)
-  - Optimized web scraper for LLM content preparation
-  - Internal API on port 11235 (not exposed via Traefik)
-  - Designed for integration with Open WebUI and n8n workflows
-  - Data persisted in `ai_crawl4ai_data` volume
-
 - **comfyui**: ComfyUI reverse proxy exposed at `comfy.ai.pivoine.art:80`
   - Nginx-based proxy to ComfyUI running on RunPod GPU server
   - Node-based UI for Flux.1 Schnell image generation workflows
@@ -727,7 +721,7 @@ Backrest backup system with restic backend:
     - Retention: 7 daily, 4 weekly, 3 monthly
 
 16. **ai-backup** (3 AM daily)
-    - Paths: `/volumes/ai_postgres_data`, `/volumes/ai_webui_data`, `/volumes/ai_crawl4ai_data`
+    - Paths: `/volumes/ai_postgres_data`, `/volumes/ai_webui_data`
     - Retention: 7 daily, 4 weekly, 6 monthly, 2 yearly
 
 17. **asciinema-backup** (11 AM daily)
@@ -738,8 +732,7 @@ Backrest backup system with restic backend:
 All Docker volumes are mounted read-only to `/volumes/` with prefixed names (e.g., `backup_core_postgres_data`) to avoid naming conflicts with other compose stacks.
 
 **Configuration Management**:
-- `config.json` template in repository defines all backup plans
-- On first run, copy config into volume: `docker cp restic/config.json restic_app:/config/config.json`
+- `core/backrest/config.json` in repository defines all backup plans (bind-mounted to container)
 - Config version must be `4` for Backrest 1.10.1 compatibility
 - Backrest manages auth automatically (username: `valknar`, password set via web UI on first access)
 
@@ -777,7 +770,7 @@ Each service uses named volumes prefixed with project name:
 - `vault_data`: Vaultwarden password vault (SQLite database)
 - `joplin_data`: Joplin note-taking data
 - `jelly_config`: Jellyfin media server configuration
-- `ai_postgres_data`, `ai_webui_data`, `ai_crawl4ai_data`: AI stack databases and application data
+- `ai_postgres_data`, `ai_webui_data`: AI stack databases and application data
 - `netdata_config`: Netdata monitoring configuration
 - `restic_data`, `restic_config`, `restic_cache`, `restic_tmp`: Backrest backup system
 - `proxy_letsencrypt_data`: SSL certificates