[Feature] Adding special information for function invoking by backend triggers.

### Search before asking

- [X] I had searched in the [issues](https://github.com/labring/laf/issues?q=is%3Aissue) and found no similar issues.

### Feature Request

I have a `__interceptor__` function to check signature from front-end (shown below). But when the triggers invoke function from back-end, it will be intercepted because of no signature.

i hope to have special mark for the invoking by triggers, or just skip `__interceptor__` like `cloud.invoke()` does.

Here is the code of my `__interceptor__` function, it will print "invalid sign" when triggers calling.

```js
import cloud from '@lafjs/cloud'
import CryptoJS from 'crypto-js';

// 检查签名是否有效
function verifySign(signKey: string, data: string, signature: string) {

// 使用HMAC-SHA256算法进行验证
const isValid = CryptoJS.HmacSHA256(data, signKey).toString() === signature;
return isValid;
}

function compareDateStrings(dateString1: string, dateString2: string, n: number): boolean {
const date1 = new Date(dateString1);
const date2 = new Date(dateString2);
const diffInSeconds = Math.abs((date1.getTime() - date2.getTime()) / 1000);
return diffInSeconds <= n;
}

export async function main(ctx: FunctionContext) {
let signKey = cloud.env.SIGN_KEY;
if (!signKey) {
// 没有开启
return true;
}
const { signdata, signstr } = ctx.headers;
const isValid = verifySign(signKey, signdata, signstr);

if (!isValid) {
console.log("invalid sign");
return false;
}

// 检查时间
const now = new Date().toISOString();
const threshold = 30; // 秒
const timeCheck = compareDateStrings(now, signdata, threshold);

if (!timeCheck) {
console.log("time check failed", now, signdata);
return false;
}

return true;
}
```

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

No files or entry points are named. Start by tracing how backend triggers invoke functions and how __interceptor__ is applied, then compare that path with cloud.invoke(). Done means trigger-originated calls have the intended special handling without disabling signature checks for frontend requests.

Written by the indexing model from the issue text.