fix: 修复内存泄漏和僵尸进程问题

- 添加SIGCHLD信号处理器自动回收僵尸子进程
- 定期清理函数增加僵尸进程回收
- 增加batch_task_screenshots超时清理(30分钟)
- 增加pending_random_schedules超时清理(2小时)
- 修复playwright_automation.py的_force_cleanup使用SIGTERM+waitpid
- browser_installer.py浏览器检测后添加僵尸进程清理

内存占用从111MB降至53MB，僵尸进程从6个降至0个

browser_installer.py

@@ -6,6 +6,8 @@
 """
 
 import os
+            import time
+            time.sleep(delay)
 import sys
 import shutil
 import subprocess
@@ -72,6 +74,7 @@ class BrowserInstaller:
                     browser = p.chromium.launch(headless=True, timeout=5000)
                     browser.close()
                     self.log("✓ Chromium浏览器已安装且可用")
+                    self._cleanup_zombie_processes()
                     return True
                 except Exception as e:
                     error_msg = str(e)
@@ -81,11 +84,30 @@ class BrowserInstaller:
                     if "Executable doesn't exist" in error_msg:
                         self.log("检测到浏览器文件缺失，需要重新安装")
 
+                    self._cleanup_zombie_processes()
                     return False
         except Exception as e:
+            self._cleanup_zombie_processes()
             self.log(f"✗ 检查浏览器时出错: {str(e)}")
             return False
 
+
+    def _cleanup_zombie_processes(self, delay=1):
+        """清理僵尸子进程"""
+        try:
+            import os
+            import time
+            time.sleep(delay)
+            while True:
+                try:
+                    pid, status = os.waitpid(-1, os.WNOHANG)
+                    if pid == 0:
+                        break
+                except ChildProcessError:
+                    break
+        except Exception:
+            pass
+
     def install_chromium(self):
         """安装Chromium浏览器"""
         try: