Password from the nightly keystore doesn't work

### Steps to reproduce

1. `./gradlew assembleFdroidNightly`

### Outcome

#### What did you expect?

Nightly builds

#### What happened instead?

```
> A failure occurred while executing com.android.build.gradle.tasks.PackageAndroidArtifact$IncrementalSplitterRunnable
> com.android.ide.common.signing.KeytoolException: Failed to read key Secret from store "/home/user/element-x-android/app/signature/nightly.keystore": Keystore was tampered with, or password was incorrect
```

Can you please regenerate the keystore with a correct password, or at least provide some fallback (or just don't store it there if it's a secret)?
I know that I can use my own keystore, but then I'll always have uncommited changes, and it'll be much more convenient to have it right in the repo. Debug builds are too slow and laggy for testing on old phones.

### Your phone model

_No response_

### Operating system version

_No response_

### Application version and app store

_No response_

### Homeserver

_No response_

### Will you send logs?

No

### Will you submit a Pull Request?

No

Start by running ./gradlew assembleFdroidNightly and inspect app/signature/nightly.keystore and the signing configuration it uses. Done means the F-Droid nightly build can be assembled without the reported password error, with a documented fallback if the keystore cannot be shared.

Written by the indexing model from the issue text.