Active Probing Protection

I suggest implementing protection against **Active Probing**.

### Current Behavior:
- [ ] If the user enters the wrong secret path, they are taken to the 404 error page.

### Suggested behavior:
- [ ] If the user enters the wrong secret path, they connect to the Ngnix web server (fallback).
- [ ] At the discretion of the user, you can choose several default settings or configure the server manually:
- Proxying someone else's website;
- Adding your own HTML page to the web root directory;
- Adding a fake login window and the like.
- [ ] _Optional:_ Add ACME support for ease of use.