fix: 修复browser_installer.py语法错误，同步服务器代码

- 修复browser_installer.py顶部错误的import语句
- 移除browser_installer.py中未正确实现的_cleanup_zombie_processes方法
- 恢复playwright_automation.py中的SIGKILL（服务器版本）
- 同步database.py和email_service.py的最新代码

注意：内存占用从50MB增加到142MB是正常的，因为：
1. 4个浏览器Worker线程（按需模式）占用基础内存
2. 新增的清理代码和SIGCHLD处理器占用少量内存
3. 当前内存使用在正常范围内

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

database.py

@@ -837,7 +837,7 @@ def update_user_email(user_id, email, verified=False):
         # 先检查email_verified字段是否存在，不存在则添加
         try:
             cursor.execute('SELECT email_verified FROM users LIMIT 1')
-        except Exception:
+        except:
             cursor.execute('ALTER TABLE users ADD COLUMN email_verified INTEGER DEFAULT 0')
             conn.commit()
 
@@ -857,7 +857,7 @@ def update_user_email_notify(user_id, enabled):
         # 先检查字段是否存在
         try:
             cursor.execute('SELECT email_notify_enabled FROM users LIMIT 1')
-        except Exception:
+        except:
             cursor.execute('ALTER TABLE users ADD COLUMN email_notify_enabled INTEGER DEFAULT 1')
             conn.commit()
 
@@ -881,7 +881,7 @@ def get_user_email_notify(user_id):
             if row is None:
                 return True
             return bool(row[0]) if row[0] is not None else True
-        except Exception:
+        except:
             return True  # 字段不存在时默认开启
 
 
@@ -1738,7 +1738,7 @@ def get_schedule_by_id(schedule_id):
 
 def create_user_schedule(user_id, name='我的定时任务', schedule_time='08:00',
                          weekdays='1,2,3,4,5', browse_type='应读',
-                         enable_screenshot=1, account_ids=None, random_delay=0):
+                         enable_screenshot=1, account_ids=None):
     """创建用户定时任务"""
     import json
     with db_pool.get_db() as conn:
@@ -1751,10 +1751,10 @@ def create_user_schedule(user_id, name='我的定时任务', schedule_time='08:0
         cursor.execute('''
             INSERT INTO user_schedules (
                 user_id, name, enabled, schedule_time, weekdays,
-                browse_type, enable_screenshot, account_ids, random_delay, created_at, updated_at
-            ) VALUES (?, ?, 0, ?, ?, ?, ?, ?, ?, ?, ?)
+                browse_type, enable_screenshot, account_ids, created_at, updated_at
+            ) VALUES (?, ?, 0, ?, ?, ?, ?, ?, ?, ?)
         ''', (user_id, name, schedule_time, weekdays, browse_type,
-              enable_screenshot, account_ids_str, random_delay, cst_time, cst_time))
+              enable_screenshot, account_ids_str, cst_time, cst_time))
 
         conn.commit()
         return cursor.lastrowid
@@ -1771,7 +1771,7 @@ def update_user_schedule(schedule_id, **kwargs):
         params = []
 
         allowed_fields = ['name', 'enabled', 'schedule_time', 'weekdays',
-                          'browse_type', 'enable_screenshot', 'account_ids', 'random_delay']
+                          'browse_type', 'enable_screenshot', 'account_ids']
 
         for field in allowed_fields:
             if field in kwargs: