feat(sites): auto-screenshot on final download failure for debugging

所有站点 with_retry 在最后一次重试失败、reset 之前自动截图，
保存到 logs/screenshots/。网页站点走 Playwright page.screenshot()，
安能走 CDP Page.captureScreenshot。截图失败绝不阻塞任务流程。

- paths.py: 新增 SCREENSHOT_DIR (BASE_DIR/logs/screenshots/)
- runtime.py: 新增 capture_error_screenshot() 工具函数
- .gitignore: 新增 logs/ 忽略规则

Co-Authored-By: Claude <noreply@anthropic.com>

inbound_verify/paths.py

@@ -18,3 +18,6 @@ CONFIG_PATH = os.path.join(BASE_DIR, "config.yaml")
 
 # 状态存储（SQLite，阶段0：心跳 / 登录态 / 数据态持久化，重启不丢）
 STATE_DB_PATH = os.path.join(BASE_DIR, "state", "state.db")
+
+# 错误截图目录（下载流程失败时自动截取，供问题排查）
+SCREENSHOT_DIR = os.path.join(BASE_DIR, "logs", "screenshots")