feat: Seedance 视频/音频改用 R2 预签名上传，移除插件内凭证

- 新增 utils/r2_uploader.py：通过 o1key 后端预签名接口上传视频/音频，零 R2 凭证
- seedance_video.py：视频、音频均改为 await upload_video/upload_audio，移除 base64 inline 编码
- 删除 doubao-seedance-2-0-fast 模型选项
- .config 加入 .gitignore，停止 git 追踪，防止 API Key 泄露
- base_client.py：新增系统代理自动检测（Windows 注册表 / macOS networksetup）

clients/openai_client.py

@@ -632,7 +632,14 @@ class OpenAIAPIClient(BaseAPIClient):
         else:
             download_info = img_size_str
 
-        print(f"{task_prefix} 请求 {size_str} → API {request_time:.1f}s → {download_info} ✓")
+        timing = response.get("_timing", {})
+        net_connect = timing.get("connect_time")
+        net_download = timing.get("download_time")
+        if net_connect is not None and net_download is not None:
+            net_str = f" | 连接 {net_connect:.2f}s | 下载 {net_download:.2f}s"
+        else:
+            net_str = ""
+        print(f"{task_prefix} 请求 {size_str} → API {request_time:.1f}s → {download_info} ✓{net_str}")
 
         total_time = time.time() - total_start
         timing_info = {