feat: add dedicated CivitAI NSFW model downloader

- Add models_civitai.yaml with 6 NSFW SDXL checkpoints
- Create artifact_civitai_download.sh with beautiful purple/magenta CLI
- Update .env.example with CIVITAI_API_KEY documentation
- Update CLAUDE.md with CivitAI usage instructions
- Rename comfyui_models.yaml to models_huggingface.yaml for clarity

Features:
- Dedicated config and downloader for CivitAI models
- Same elegant architecture as HuggingFace downloader
- Retry logic, rate limiting, progress bars
- Models: LUSTIFY, Pony Diffusion V6, RealVisXL, etc.

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

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

.env.example

@@ -15,10 +15,33 @@ HF_TOKEN=hf_your_token_here
 # Get it with: tailscale ip -4
 # GPU_TAILSCALE_IP=100.100.108.13
 
+# ============================================================================
+# CivitAI API Key (Optional, for NSFW models)
+# ============================================================================
+# Get your API key from: https://civitai.com/user/account
+# Required for downloading NSFW models with artifact_civitai_download.sh
+# CIVITAI_API_KEY=your_civitai_api_key_here
+
+# ============================================================================
+# Tailscale VPN (Optional, for remote access)
+# ============================================================================
+# Get your authkey from: https://login.tailscale.com/admin/settings/keys
+# TAILSCALE_AUTHKEY=tskey-auth-your_tailscale_authkey_here
+
+# ============================================================================
+# WebDAV Sync (Optional, for output synchronization)
+# ============================================================================
+# WebDAV credentials for syncing ComfyUI outputs to cloud storage
+# WEBDAV_URL=https://webdav.example.com/
+# WEBDAV_USERNAME=your_username
+# WEBDAV_PASSWORD=your_password
+# WEBDAV_REMOTE_PATH=/path/to/comfyui/outputs
+
 # ============================================================================
 # Notes
 # ============================================================================
 # - HF_TOKEN is the only required variable for basic operation
+# - CIVITAI_API_KEY is required for downloading NSFW models from CivitAI
 # - Models will be cached in /workspace/ directories on RunPod
 # - Orchestrator automatically manages model switching
 # - No database credentials needed (stateless architecture)