fix(RetryManager): 修复重试逻辑中的 Base64 编码崩溃问题

- 增加了对 html_render 返回本地文件路径的处理 (读取为 bytes)
- 增加了对渲染结果的文件头校验，避免处理错误文本

src/infrastructure/scheduler/retry.py

@@ -161,21 +161,39 @@ class RetryManager:
             )
 
             # Fix: html_render might return URL (str) even if return_url=False in some implementations
-            if isinstance(image_data, str) and image_data.startswith(
-                ("http://", "https://")
-            ):
-                logger.warning(
-                    f"[RetryManager] html_render 返回了 URL 而不是 bytes，尝试下载: {image_data}"
-                )
-                async with aiohttp.ClientSession() as session:
-                    async with session.get(image_data) as resp:
-                        if resp.status == 200:
-                            image_data = await resp.read()
+            if isinstance(image_data, str):
+                if image_data.startswith(("http://", "https://")):
+                    logger.warning(
+                        f"[RetryManager] html_render 返回了 URL 而不是 bytes，尝试下载: {image_data}"
+                    )
+                    async with aiohttp.ClientSession() as session:
+                        async with session.get(image_data) as resp:
+                            if resp.status == 200:
+                                image_data = await resp.read()
+                            else:
+                                logger.error(
+                                    f"[RetryManager] 下载重试图片失败: {resp.status}"
+                                )
+                                image_data = None
+                else:
+                    # 本地文件路径
+                    try:
+                        import os
+                        if os.path.exists(image_data):
+                            with open(image_data, "rb") as f:
+                                image_data = f.read()
+                            
+                            # 校验文件头 (防御性编程，避免发送错误文本)
+                            if not image_data.startswith(b"\xff\xd8") and not image_data.startswith(b"\x89PNG"):
+                                if len(image_data) < 1024 and (b"Error" in image_data or b"Exception" in image_data):
+                                    logger.error(f"[RetryManager] 渲染器生成了错误文件而非图片: {image_data.decode('utf-8', errors='ignore')}")
+                                    return False
                         else:
-                            logger.error(
-                                f"[RetryManager] 下载重试图片失败: {resp.status}"
-                            )
+                            logger.error(f"[RetryManager] 渲染器返回的路径不存在: {image_data}")
                             image_data = None
+                    except Exception as e:
+                        logger.error(f"[RetryManager] 读取本地图片失败: {e}")
+                        image_data = None
 
             if not image_data:
                 logger.warning(