Extra improvements for the UI of the Alert mini-widget

[rafaellehmkuhl]

Some review notes, before I forget:

• It would be nice if the alert levels (like "WARNING"/"INFO"/etc) used the corresponding level colour
• Ideally the colours would be defined as part of a theme stylesheet
  • If that's not possible/practical then I think they should be defined as part of the alert type
• I think the warnings should also be persistently highlighted, not just the errors and critical

Originally posted by @ES-Alexander in #2251 (comment)

[rafaellehmkuhl]

Extra:

• Make extra space for the hovering lock icon
• Make it so the expanded rows have the same width as the always-visible row
• Add some extra vertical spacing between the always-visible row and the expanded card so it does not start exactly at the end of the top-bar (looks weird)

[ES-Alexander]

• Allow it to expand upwards when it's in the bottom bar (or maybe just the bottom half of the screen, or maybe with a user config toggle for "open upwards")