fix: AGNES图像/视频生成强制经智能路由代理(172.18.0.1:7890)，修复容器内直连被重置导致图像生成异常

backend/python/app/api/chat.py

@@ -79,6 +79,14 @@ def _html_escape(s: str) -> str:
             .replace('"', """).replace("'", "'"))
 
 
+def _outbound_proxy() -> str:
+    """出网代理地址。容器内直连 apihub.agnes-ai.com 会被对端重置
+    (httpx RemoteProtocolError: Server disconnected without sending a response)，
+    必须经 172.18.0.1:7890 智能路由代理(其对国内 AGNES 域名走直连)。"""
+    import os
+    return os.environ.get("HTTPS_PROXY") or os.environ.get("HTTP_PROXY") or "http://172.18.0.1:7890"
+
+
 async def _generate_media(db, ai_model, prompt: str, user_id: str = None) -> str:
     """图像/视频生成模型统一入口：按 capabilities 调用 AGNES 等媒体生成 API。
     返回可直接在 AI 聊天中渲染的富文本(含 <img>/<video> 标签)。"""
@@ -105,7 +113,7 @@ async def _generate_media(db, ai_model, prompt: str, user_id: str = None) -> str
             "extra_body": {"response_format": "url"},
         }
         try:
-            async with httpx.AsyncClient(timeout=timeout) as client:
+            async with httpx.AsyncClient(timeout=timeout, proxy=_outbound_proxy()) as client:
                 resp = await client.post(api_url, headers=headers, json=payload)
             if resp.status_code != 200:
                 return f"⚠️ 图像生成失败 (HTTP {resp.status_code}): {resp.text[:200]}"
@@ -141,7 +149,7 @@ async def _generate_media(db, ai_model, prompt: str, user_id: str = None) -> str
             "frame_rate": 24,
         }
         try:
-            async with httpx.AsyncClient(timeout=timeout) as client:
+            async with httpx.AsyncClient(timeout=timeout, proxy=_outbound_proxy()) as client:
                 resp = await client.post(api_url, headers=headers, json=payload)
                 if resp.status_code != 200:
                     return f"⚠️ 视频生成失败 (HTTP {resp.status_code}): {resp.text[:200]}"