Improve flow for iOS - browser selection

### Problem

At the moment, it is unknown which browser the user is using if the screenshot does not include elements of the browser interface.

### Proposed solution

Display a list of browsers so that we know for sure that a compatible browser is being used - Safari.
Some users deliberately use other browsers, relying solely on DNS filtering.
If not Safari is selected, display a warning that full filtering is only possible in Safari. Without prohibiting continuation.

It may be worth adding a warning confirming that the user is aware of the restrictions but still wants to continue (in this case, filter developers will inspect the site for unblocked ad and tracking domains).

Original issue:
https://github.com/AdguardTeam/AdguardFilters/issues/216761#issuecomment-3506177087