feat: 实现通知渠道管理功能

- 新增 platform_notification_channels 表管理通知渠道（钉钉/企微机器人）
- 新增通知渠道管理页面，支持创建、编辑、测试、删除
- 定时任务增加通知渠道选择和企微应用选择
- 脚本执行支持返回值（result变量），自动发送到配置的渠道
- 调度器执行脚本后根据配置自动发送通知

使用方式：
1. 在「通知渠道」页面为租户配置钉钉/企微机器人
2. 创建定时任务时选择通知渠道
3. 脚本中设置 result = {'content': '内容', 'title': '标题'}
4. 任务执行后自动发送到配置的渠道

backend/app/routers/notification_channels.py

@@ -0,0 +1,181 @@
+"""通知渠道API路由"""
+from typing import Optional, List
+from fastapi import APIRouter, Depends, HTTPException, Query
+from pydantic import BaseModel
+from sqlalchemy.orm import Session
+from sqlalchemy import desc
+
+from ..database import get_db
+from ..models.notification_channel import NotificationChannel
+
+
+router = APIRouter(prefix="/api/notification-channels", tags=["notification-channels"])
+
+
+# ==================== Schemas ====================
+
+class ChannelCreate(BaseModel):
+    tenant_id: str
+    channel_name: str
+    channel_type: str  # dingtalk_bot, wecom_bot
+    webhook_url: str
+    description: Optional[str] = None
+
+
+class ChannelUpdate(BaseModel):
+    channel_name: Optional[str] = None
+    channel_type: Optional[str] = None
+    webhook_url: Optional[str] = None
+    description: Optional[str] = None
+    is_enabled: Optional[bool] = None
+
+
+# ==================== CRUD ====================
+
+@router.get("")
+async def list_channels(
+    tenant_id: Optional[str] = None,
+    channel_type: Optional[str] = None,
+    is_enabled: Optional[bool] = None,
+    page: int = Query(1, ge=1),
+    size: int = Query(50, ge=1, le=100),
+    db: Session = Depends(get_db)
+):
+    """获取通知渠道列表"""
+    query = db.query(NotificationChannel)
+    
+    if tenant_id:
+        query = query.filter(NotificationChannel.tenant_id == tenant_id)
+    if channel_type:
+        query = query.filter(NotificationChannel.channel_type == channel_type)
+    if is_enabled is not None:
+        query = query.filter(NotificationChannel.is_enabled == is_enabled)
+    
+    total = query.count()
+    items = query.order_by(desc(NotificationChannel.created_at)).offset((page - 1) * size).limit(size).all()
+    
+    return {
+        "total": total,
+        "items": [format_channel(c) for c in items]
+    }
+
+
+@router.get("/{channel_id}")
+async def get_channel(channel_id: int, db: Session = Depends(get_db)):
+    """获取渠道详情"""
+    channel = db.query(NotificationChannel).filter(NotificationChannel.id == channel_id).first()
+    if not channel:
+        raise HTTPException(status_code=404, detail="渠道不存在")
+    return format_channel(channel)
+
+
+@router.post("")
+async def create_channel(data: ChannelCreate, db: Session = Depends(get_db)):
+    """创建通知渠道"""
+    channel = NotificationChannel(
+        tenant_id=data.tenant_id,
+        channel_name=data.channel_name,
+        channel_type=data.channel_type,
+        webhook_url=data.webhook_url,
+        description=data.description,
+        is_enabled=True
+    )
+    
+    db.add(channel)
+    db.commit()
+    db.refresh(channel)
+    
+    return {"success": True, "id": channel.id}
+
+
+@router.put("/{channel_id}")
+async def update_channel(channel_id: int, data: ChannelUpdate, db: Session = Depends(get_db)):
+    """更新通知渠道"""
+    channel = db.query(NotificationChannel).filter(NotificationChannel.id == channel_id).first()
+    if not channel:
+        raise HTTPException(status_code=404, detail="渠道不存在")
+    
+    if data.channel_name is not None:
+        channel.channel_name = data.channel_name
+    if data.channel_type is not None:
+        channel.channel_type = data.channel_type
+    if data.webhook_url is not None:
+        channel.webhook_url = data.webhook_url
+    if data.description is not None:
+        channel.description = data.description
+    if data.is_enabled is not None:
+        channel.is_enabled = data.is_enabled
+    
+    db.commit()
+    return {"success": True}
+
+
+@router.delete("/{channel_id}")
+async def delete_channel(channel_id: int, db: Session = Depends(get_db)):
+    """删除通知渠道"""
+    channel = db.query(NotificationChannel).filter(NotificationChannel.id == channel_id).first()
+    if not channel:
+        raise HTTPException(status_code=404, detail="渠道不存在")
+    
+    db.delete(channel)
+    db.commit()
+    return {"success": True}
+
+
+@router.post("/{channel_id}/test")
+async def test_channel(channel_id: int, db: Session = Depends(get_db)):
+    """测试通知渠道"""
+    import httpx
+    
+    channel = db.query(NotificationChannel).filter(NotificationChannel.id == channel_id).first()
+    if not channel:
+        raise HTTPException(status_code=404, detail="渠道不存在")
+    
+    test_content = f"**测试消息**\n\n渠道名称: {channel.channel_name}\n发送时间: 测试中..."
+    
+    try:
+        if channel.channel_type == 'dingtalk_bot':
+            payload = {
+                "msgtype": "markdown",
+                "markdown": {
+                    "title": "渠道测试",
+                    "text": test_content
+                }
+            }
+        else:  # wecom_bot
+            payload = {
+                "msgtype": "markdown",
+                "markdown": {
+                    "content": test_content
+                }
+            }
+        
+        async with httpx.AsyncClient(timeout=10) as client:
+            response = await client.post(channel.webhook_url, json=payload)
+            result = response.json()
+            
+            # 钉钉返回 errcode=0，企微返回 errcode=0
+            if result.get('errcode') == 0:
+                return {"success": True, "message": "发送成功"}
+            else:
+                return {"success": False, "message": f"发送失败: {result}"}
+    
+    except Exception as e:
+        return {"success": False, "message": f"发送失败: {str(e)}"}
+
+
+# ==================== Helpers ====================
+
+def format_channel(channel: NotificationChannel) -> dict:
+    """格式化渠道数据"""
+    return {
+        "id": channel.id,
+        "tenant_id": channel.tenant_id,
+        "channel_name": channel.channel_name,
+        "channel_type": channel.channel_type,
+        "webhook_url": channel.webhook_url,
+        "description": channel.description,
+        "is_enabled": channel.is_enabled,
+        "created_at": channel.created_at,
+        "updated_at": channel.updated_at
+    }