Improve Badging / Browser Notifications

[NickM-27]

We can improve the browser notifications experience with the following improvements:

• For PWAs we can use the badge API in the frontend and backend (if notifications are enabled) to have the home screen show the number of unreviewed alerts for the current day
• We can use one of a few approaches to show a red dot or some indicator on the favicon indicating that there are unreviewed alerts (similar to unread discord messages) to more easily indicate when something happened without needing to switch to the Frigate tab