Allowed Sites list: IP address entries silently vanish or get duplicated

Summary
Adding an IP address (e.g. a local network preview URL like 192.168.1.73, generated by a dev tool such as Prepros for LAN/mobile preview) to Settings -> Browser -> Allowed Sites does not behave like adding a domain. No error is shown, but the entry either:

• silently disappears from the list after being added (not shown on reopening the dialog), or
• ends up duplicated (the same IP listed twice after retrying).

Steps to reproduce

1. Open Settings -> Browser -> Erlaubte Seiten.
2. Add an IP address (e.g. 192.168.1.73) via the "add URL" field.
3. Close and reopen the dialog.
4. Entry is missing, or (after retrying) appears twice.

Expected
IP addresses should be accepted the same way domains are: added once, persisted, not silently dropped or duplicated. If IPs are intentionally unsupported, the UI should show a validation error instead of failing silently.