fix: restore ComfyUI as workflow frontend with BoosAPI backend integration

ComfyUI is kept as a visual workflow editor (node-based). All actual
generation goes through BoosAPI's own API via boosapi_comfy_nodes.py
custom nodes (now defaulting to localhost:4000/v1).

Architecture:
  BoosAPI (Node.js, port 4000)
    ├── /video-agent → iframe → ComfyUI (Python, port 8188, CPU)
    │                              └── custom_nodes/boosapi_comfy_nodes.py
    │                                   └── calls BoosAPI /v1/... API
    ├── /comfyui-agent → chat interface (direct API calls)
    └── /v1/... → API endpoints (LLM, image, TTS, video)

Signed-off-by: boos <boos@boos.lat>

src/web/pages/ComfyUI.tsx

@@ -1,8 +1,15 @@
 import React from 'react';
 
 export default function ComfyUI() {
+  const [isDark, setIsDark] = React.useState(true);
+
   React.useEffect(() => {
-    window.location.href = '/comfyui-agent';
+    const el = document.documentElement;
+    const check = () => setIsDark(el.getAttribute('data-theme') !== 'light');
+    check();
+    const mo = new MutationObserver(check);
+    mo.observe(el, { attributes: true, attributeFilter: ['data-theme'] });
+    return () => mo.disconnect();
   }, []);
 
   return (
@@ -11,14 +18,20 @@ export default function ComfyUI() {
         width: '100%',
         height: 'calc(100vh - 56px)',
         display: 'flex',
-        alignItems: 'center',
-        justifyContent: 'center',
-        background: 'var(--color-bg, #0f0f1a)',
-        color: 'var(--color-text-secondary, #888)',
-        fontSize: '16px',
+        flexDirection: 'column',
+        background: isDark ? '#1a1a2e' : '#f5f5f5',
       }}
     >
-      🔄 正在跳转至 AI 视频助手...
+      <iframe
+        src="/comfyui"
+        style={{
+          width: '100%',
+          height: '100%',
+          border: 'none',
+        }}
+        title="ComfyUI"
+        allow="clipboard-read; clipboard-write"
+      />
     </div>
   );
 }