feat: initial ComfyUI workflow templates extension

- 40 workflow templates (text-to-image, image-to-video, image-to-image,
  text-to-music, upscaling, advanced, nsfw)
- Color-coded placeholder preview images using Pillow
- Template-only extension (no custom nodes)
- Preview generation script for future workflow additions

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

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

README.md

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+# ComfyUI Extras
+
+Curated workflow templates for ComfyUI.
+
+## Installation
+
+Clone into your ComfyUI custom_nodes directory:
+
+```bash
+cd /path/to/ComfyUI/custom_nodes
+git clone https://github.com/valknar/comfyui-extras.git
+```
+
+Restart ComfyUI.
+
+## Usage
+
+Access workflows via **Workflow > Browse Templates** in ComfyUI.
+Look for the "ComfyUI Extras" category.
+
+## Included Workflows (40 total)
+
+### Text-to-Image (5 workflows)
+- FLUX Dev / Schnell
+- SD 3.5 Large
+- SDXL with Refiner
+- LoRA Fusion
+
+### Image-to-Video (13 workflows)
+- CogVideoX
+- SVD / SVD-XT
+- Wan 2.2 (multiple variants)
+- HunyuanVideo
+
+### Image-to-Image (3 workflows)
+- IPAdapter Style
+- IPAdapter Face
+- IPAdapter Composition
+
+### Text-to-Music (9 workflows)
+- MusicGen (Small/Medium/Large/Melody)
+- AceStep
+- DiffRhythm
+
+### Upscaling (3 workflows)
+- Simple Upscale
+- Ultimate SD Upscale
+- Face Upscale
+
+### Advanced (3 workflows)
+- AnimateDiff
+- ControlNet Fusion
+- Batch Pipeline
+
+### NSFW (4 workflows)
+- Lustify Realistic
+- RealVisXL Lightning
+- Pony Anime
+- NSFW Ultimate Upscale
+
+## Requirements
+
+Each workflow requires specific models to be installed.
+Check each workflow for model requirements.
+
+## Regenerating Preview Images
+
+If you modify workflows, regenerate previews:
+
+```bash
+pip install Pillow
+python scripts/generate_previews.py
+```
+
+## License
+
+MIT