Certificate expiry warning should be relative to the certificate's validity

### Prerequisites

- [x] I have checked the [Wiki](https://github.com/AdguardTeam/AdGuardHome/wiki) and [Discussions](https://github.com/AdguardTeam/AdGuardHome/discussions) and found no answer

- [x] I have searched other issues and found no duplicates

- [x] I want to request a feature or enhancement and not ask a question

### The problem

Let's Encrypt [recently](https://community.letsencrypt.org/t/upcoming-changes-to-let-s-encrypt-certificates/243873) made the ability to request IP based certificates available to everyone, provided a [shortlived](https://letsencrypt.org/docs/profiles/#shortlived) profile is used, limiting certificate expiry to 160 hours (or 6d6h).

However, the yellow `Your SSL certificate is about to expire` warning at the top of the page is [hardcoded to appear 5 days before expiry](https://github.com/AdguardTeam/AdGuardHome/blob/v0.107.71/client/src/components/ui/EncryptionTopline.tsx#L29).

Let's Encrypt's [guidelines](https://letsencrypt.org/docs/integration-guide/#when-to-renew) recommend certificates be renewed with a third of its lifetime left, and certificates valid for under 10 days be renewed with half its lifetime left. While not everyone may be using Let's Encrypt for encryption within AGH, the guidelines are more sane than hardcoding the notification for 5 days prior to expiry.

### Proposed solution

The expiry calculation logic should be modified to account for differences in expiry time, and also display the expiry time and remaining time to make the notification a bit more useful.

### Alternatives considered and additional information

_No response_