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>

example_workflows/simple-upscale-production-v1.json

@@ -0,0 +1,207 @@
+{
+  "last_node_id": 6,
+  "last_link_id": 5,
+  "nodes": [
+    {
+      "id": 1,
+      "type": "LoadImage",
+      "pos": [50, 100],
+      "size": [350, 100],
+      "flags": {},
+      "order": 0,
+      "mode": 0,
+      "outputs": [
+        {
+          "name": "IMAGE",
+          "type": "IMAGE",
+          "links": [1],
+          "slot_index": 0
+        },
+        {
+          "name": "MASK",
+          "type": "MASK",
+          "links": null,
+          "slot_index": 1
+        }
+      ],
+      "properties": {
+        "Node name for S&R": "LoadImage"
+      },
+      "widgets_values": ["input_image.png", "image"],
+      "title": "API Input Image"
+    },
+    {
+      "id": 2,
+      "type": "UpscaleModelLoader",
+      "pos": [50, 400],
+      "size": [350, 100],
+      "flags": {},
+      "order": 1,
+      "mode": 0,
+      "outputs": [
+        {
+          "name": "UPSCALE_MODEL",
+          "type": "UPSCALE_MODEL",
+          "links": [2],
+          "slot_index": 0
+        }
+      ],
+      "properties": {
+        "Node name for S&R": "UpscaleModelLoader"
+      },
+      "widgets_values": ["RealESRGAN_x4.pth"],
+      "title": "Upscale Model Loader"
+    },
+    {
+      "id": 3,
+      "type": "ImageUpscaleWithModel",
+      "pos": [450, 100],
+      "size": [315, 100],
+      "flags": {},
+      "order": 2,
+      "mode": 0,
+      "inputs": [
+        {
+          "name": "upscale_model",
+          "type": "UPSCALE_MODEL",
+          "link": 2
+        },
+        {
+          "name": "image",
+          "type": "IMAGE",
+          "link": 1
+        }
+      ],
+      "outputs": [
+        {
+          "name": "IMAGE",
+          "type": "IMAGE",
+          "links": [3],
+          "slot_index": 0
+        }
+      ],
+      "properties": {
+        "Node name for S&R": "ImageUpscaleWithModel"
+      },
+      "title": "Upscale with Model (4x)"
+    },
+    {
+      "id": 4,
+      "type": "ImageScaleBy",
+      "pos": [800, 100],
+      "size": [315, 100],
+      "flags": {},
+      "order": 3,
+      "mode": 0,
+      "inputs": [
+        {
+          "name": "image",
+          "type": "IMAGE",
+          "link": 3
+        }
+      ],
+      "outputs": [
+        {
+          "name": "IMAGE",
+          "type": "IMAGE",
+          "links": [4, 5],
+          "slot_index": 0
+        }
+      ],
+      "properties": {
+        "Node name for S&R": "ImageScaleBy"
+      },
+      "widgets_values": ["lanczos", 0.5],
+      "title": "Optional Downscale to 2x"
+    },
+    {
+      "id": 5,
+      "type": "PreviewImage",
+      "pos": [1150, 100],
+      "size": [315, 100],
+      "flags": {},
+      "order": 4,
+      "mode": 0,
+      "inputs": [
+        {
+          "name": "images",
+          "type": "IMAGE",
+          "link": 4
+        }
+      ],
+      "properties": {
+        "Node name for S&R": "PreviewImage"
+      },
+      "title": "Preview Output"
+    },
+    {
+      "id": 6,
+      "type": "SaveImage",
+      "pos": [1150, 400],
+      "size": [315, 100],
+      "flags": {},
+      "order": 5,
+      "mode": 0,
+      "inputs": [
+        {
+          "name": "images",
+          "type": "IMAGE",
+          "link": 5
+        }
+      ],
+      "properties": {
+        "Node name for S&R": "SaveImage"
+      },
+      "widgets_values": ["simple_upscale_output"],
+      "title": "API Image Output"
+    }
+  ],
+  "links": [
+    [1, 1, 0, 3, 1, "IMAGE"],
+    [2, 2, 0, 3, 0, "UPSCALE_MODEL"],
+    [3, 3, 0, 4, 0, "IMAGE"],
+    [4, 4, 0, 5, 0, "IMAGE"],
+    [5, 4, 0, 6, 0, "IMAGE"]
+  ],
+  "groups": [],
+  "config": {},
+  "extra": {
+    "workflow_info": {
+      "name": "Simple Upscale Production",
+      "version": "1.0.0",
+      "description": "Fast, straightforward upscaling using RealESRGAN. No diffusion refinement, optimized for speed.",
+      "category": "upscaling",
+      "tags": ["simple-upscale", "fast", "realesrgan", "production"],
+      "requirements": {
+        "models": ["RealESRGAN"],
+        "custom_nodes": [],
+        "vram_min": "8GB"
+      },
+      "parameters": {
+        "input_image": {
+          "node_id": 1,
+          "type": "image",
+          "required": true
+        },
+        "model": {
+          "node_id": 2,
+          "type": "string",
+          "default": "RealESRGAN_x4.pth",
+          "options": ["RealESRGAN_x2.pth", "RealESRGAN_x4.pth"]
+        },
+        "final_scale": {
+          "node_id": 4,
+          "widget_index": 1,
+          "type": "float",
+          "default": 0.5,
+          "description": "Scale factor after 4x upscale (0.5 = final 2x, 1.0 = keep 4x)"
+        }
+      },
+      "performance": {
+        "avg_generation_time": "5-15 seconds",
+        "vram_usage": "~6-8GB"
+      }
+    }
+  },
+  "version": 0.4
+}