Task stack hijacking

### ⚠️ Before posting ⚠️

- [x] This is a **bug**, not a question or an enhancement.
- [x] I've [searched for similar issues](https://github.com/nextcloud/android/issues) and didn't find a duplicate.
- [x] I've written a clear and descriptive title for this issue, not just "Bug" or "Crash".
- [x] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/).

### Steps to reproduce

Task stack hijacking affects apps with startup modes of singletask and standard

We hijacked the task stack of the application by setting the same taskAffinity. When the user clicks on the application, what is actually displayed is the activity of the attack application we wrote (there is no interface switching process in the entire process, which is very hidden and difficult for the user to discover). By designing the activity in this way, we can mimic the login interface of the application, induce the user to log in, and steal the user's private password information

Reproduction method:
Write an attack application that hijacks the application's task stack by setting the taskAffinity attribute to the package name of soul

### Expected behaviour

Repair plan

1. Set the taskAffinity property of the application's activity to empty

2. When the APP is initially enabled, check whether the number of front-end tasks in the activity stack is greater than the initial set value. If it is greater than the initial set value, it is necessary to draw the user's attention to the possibility of disguised malicious attacks in the future. Do not output sensitive information on the page

Example code:

val activityManager = getSystemService(ACTIVITY_SERVICE) as ActivityManager

val appTasks: List = activityManager.getAppTasks()

if (appTasks.isNotEmpty()) {

Val initial Activity Count=5//Assuming that the initial set number of front-end task activities is 5

val taskInfo: RecentTaskInfo = appTasks[0].taskInfo

val numActivities: Int = taskInfo.numActivities

if (numActivities > initialActivityCount) {

//If the number of activities in the current front-end task is greater than the initial set value, a Toast prompt will pop up to remind the user to pay attention to safety

Toast.makeText (this, "Warning: The current front-end task has an abnormal number of activities, which may pose a security risk. Please be careful not to enter sensitive information on subsequent pages! ", Toast.LENGTH_LONG).show()

}

}

### Actual behaviour

We hijacked the task stack of the application by setting the same taskAffinity. When the user clicks on the application, what is actually displayed is the activity of the attack application we wrote (there is no interface switching process in the entire process, which is very hidden and difficult for the user to discover). By designing the activity in this way, we can mimic the login interface of the application, induce the user to log in, and steal the user's privacy password information. The specific attack video has been attached

[攻击视频.zip](https://github.com/user-attachments/files/19809099/default.zip)

### Android version

9.0

### Device brand and model

xiaomi 9

### Stock or custom OS?

Custom (explain in "additional information")

### Nextcloud android app version

3.1.3

### Nextcloud server version

WU

### Using a reverse proxy?

No

### Android logs

_No response_

### Server error logs

```bash

```

### Additional information

I currently don't know the version of NextCloud because we haven't logged in yet. Our hijacking occurred when we first clicked on the application