refactor: ComfyUI Agent - fix auth, upstream API, and SSE streaming

- Fix auth: use upstream API key (sk-boos4721) instead of local proxy
- Simplify SSE: remove nested SSE-in-SSE parsing, stream as plain text
- Fix frontend: add Authorization header from localStorage
- Fix ComfyUI nodes: default to api.boos.lat with correct API key
- All verified: frontend streaming works end-to-end with gpt-5.5

src/web/pages/ComfyUIAgent.tsx

@@ -53,7 +53,10 @@ export default function ComfyUIAgent() {
 
       const resp = await fetch('/api/comfyui-agent/chat', {
         method: 'POST',
-        headers: { 'Content-Type': 'application/json' },
+        headers: {
+          'Content-Type': 'application/json',
+          'Authorization': `Bearer ${localStorage.getItem('auth_token') || ''}`,
+        },
         body: JSON.stringify({ messages: apiMessages }),
         signal: abortController.signal,
       });