Pulse page improvements (#30149)

1. add border-radius and spacing to bars
2. use tailwind background classes
3. Add more space around activity list headers

<img width="983" alt="Screenshot 2024-03-27 at 23 40 54"
src="https://github.com/go-gitea/gitea/assets/115237/70f72c30-e69f-4ecb-882f-32b8bc94d638">
<img width="1020" alt="Screenshot 2024-03-27 at 23 41 02"
src="https://github.com/go-gitea/gitea/assets/115237/a35dbbda-515c-40b0-938a-d759f9686b8e">

web_src/css/dashboard.css

@@ -7,7 +7,6 @@
 .dashboard.feeds .context.user.menu .ui.header,
 .dashboard.issues .context.user.menu .ui.header {
   font-size: 1rem;
-  text-transform: none;
 }
 
 .dashboard.feeds .filter.menu,