Lock the app after multiple unsuccessful attempts to open vault

### Checks

- [x] I have read the Wiki, searched the open issues, and still think this is a new feature.

### Explain the problem clearly and succinctly:

I'm using a 2FA app that has this security feature. I thought it might be a good idea for KeePassDX to offer it too. The feature guards against repeated malicious attempts to unlock database (open vault). This would be a scenario where someone gets access to your device and tries to open your Keepass database by trying various passwords.

### Describe the solution you'd like:

I suggest that the app self locks for a period of time after multiple unsuccessful attempts at opening a vault. The app user can choose in Settings a) the number of wrong password entries that will trigger a lockout (e.g. 3, 5, etc.) and b) the lockout time (e.g. 5 minutes, 10, 30, 60, etc.)

### Describe alternatives you've considered:

_No response_

### Additional context:

_No response_

No files, tests, or entry points are named. Start by tracing the vault-opening flow and the Settings area, then define how failed attempts, configurable thresholds, and lockout durations should be stored and enforced; done means repeated incorrect passwords trigger the selected lockout and valid unlocking works again afterward.

Written by the indexing model from the issue text.