theme: Lock screen notification style tweaks

- use standard border radius for notifications
- negative space pills for counters
- no border, slightly less opaque background allowed
  by the massive blur radius for the wallpaper

!998
6 jobs for !998 with wip/jimmac/lock-screen-notifications in 5 minutes and 18 seconds (queued for 2 seconds)
detached
Status Job ID Name Coverage
  Review
passed #592427
check_commit_log

00:00:21

passed #592429
eslint

00:01:09

passed #592428
js_check

00:00:29

 
  Build
passed #592430
build

00:02:28

 
  Test
passed #592431
test

00:01:15

passed #592432
test-pot

00:01:40