feat: 实现定时任务系统

- 新增 platform_scheduled_tasks, platform_task_logs, platform_script_vars, platform_secrets 数据库表
- 实现 ScriptSDK 提供 AI/通知/DB/HTTP/变量存储/参数获取等功能
- 实现安全的脚本执行器，支持沙箱环境和禁止危险操作
- 实现 APScheduler 调度服务，支持简单时间点和 CRON 表达式
- 新增定时任务 API 路由，包含 CRUD、执行、日志、密钥管理
- 新增定时任务前端页面，支持脚本编辑、测试运行、日志查看

backend/app/models/scheduled_task.py

@@ -0,0 +1,96 @@
+"""定时任务相关模型"""
+from datetime import datetime
+from sqlalchemy import Column, BigInteger, Integer, String, Text, Enum, SmallInteger, TIMESTAMP, DateTime
+from ..database import Base
+
+
+class ScheduledTask(Base):
+    """定时任务表"""
+    __tablename__ = "platform_scheduled_tasks"
+    
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    tenant_id = Column(String(50))
+    task_name = Column(String(100), nullable=False)
+    task_type = Column(Enum('webhook', 'script'), nullable=False, default='script')
+    
+    # 调度配置
+    schedule_type = Column(Enum('simple', 'cron'), nullable=False, default='simple')
+    time_points = Column(Text)  # JSON数组 ["08:00", "12:00"]
+    cron_expression = Column(String(100))
+    
+    # Webhook配置
+    webhook_url = Column(String(500))
+    webhook_method = Column(String(10), default='POST')
+    webhook_headers = Column(Text)  # JSON格式
+    
+    # 脚本配置
+    script_content = Column(Text)
+    script_timeout = Column(Integer, default=300)
+    
+    # 输入参数
+    input_params = Column(Text)  # JSON格式
+    
+    # 重试配置
+    retry_count = Column(Integer, default=0)
+    retry_interval = Column(Integer, default=60)
+    
+    # 告警配置
+    alert_on_failure = Column(SmallInteger, default=0)
+    alert_webhook = Column(String(500))
+    
+    # 状态
+    status = Column(SmallInteger, default=1)  # 0-禁用 1-启用
+    last_run_at = Column(DateTime)
+    last_run_status = Column(String(20))
+    
+    created_at = Column(TIMESTAMP, default=datetime.now)
+    updated_at = Column(TIMESTAMP, default=datetime.now, onupdate=datetime.now)
+
+
+class TaskLog(Base):
+    """任务执行日志"""
+    __tablename__ = "platform_task_logs"
+    
+    id = Column(BigInteger, primary_key=True, autoincrement=True)
+    task_id = Column(Integer, nullable=False)
+    tenant_id = Column(String(50))
+    trace_id = Column(String(100))
+    
+    status = Column(Enum('running', 'success', 'failed'), nullable=False)
+    started_at = Column(DateTime, nullable=False)
+    finished_at = Column(DateTime)
+    duration_ms = Column(Integer)
+    
+    output = Column(Text)
+    error = Column(Text)
+    retry_count = Column(Integer, default=0)
+    
+    created_at = Column(TIMESTAMP, default=datetime.now)
+
+
+class ScriptVar(Base):
+    """脚本变量存储"""
+    __tablename__ = "platform_script_vars"
+    
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    task_id = Column(Integer, nullable=False)
+    tenant_id = Column(String(50))
+    var_key = Column(String(100), nullable=False)
+    var_value = Column(Text)  # JSON格式
+    
+    created_at = Column(TIMESTAMP, default=datetime.now)
+    updated_at = Column(TIMESTAMP, default=datetime.now, onupdate=datetime.now)
+
+
+class Secret(Base):
+    """密钥管理"""
+    __tablename__ = "platform_secrets"
+    
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    tenant_id = Column(String(50))  # NULL为全局
+    secret_key = Column(String(100), nullable=False)
+    secret_value = Column(Text, nullable=False)
+    description = Column(String(255))
+    
+    created_at = Column(TIMESTAMP, default=datetime.now)
+    updated_at = Column(TIMESTAMP, default=datetime.now, onupdate=datetime.now)