Issue sidebar and misc css fixes (#15524)

- Replace remaining font icons with SVG in issue sidebar
- Rework issue due date display
- Realign avatar in timeline
- Fix font size in repo search and code explore
- Consolidate active button styles
- Fix loading form on arc-green
- Align time tracker buttons vertically

Fixes: https://github.com/go-gitea/gitea/issues/15896

web_src/less/helpers.less

@@ -24,7 +24,6 @@
 
 .word-break {
   word-wrap: break-word !important;
-  word-break: break-all !important;
 }
 
 .full-screen-width { width: 100vw !important; }