Remove dead CSS rules (#37173) (#37177)

Backport #37173 by @silverwind

Remove CSS rules whose HTML classes/IDs are no longer referenced in any
template, Go source, or JavaScript/TypeScript file:

- `.archived-icon`: removed from templates in c85bb62635
- `.bottom-line`: removed from blame rendering in 9c6aeb47f7
- `.commit-status-link`: removed from templates in f3c4baa84b
- `.instruct-toggle`: removed from templates in 75e85c25c1
- `.runner-new-text`, `#runner-new`: never referenced outside CSS
- `.ap-terminal`: stale, asciinema-player uses `.ap-term`, still not
needed
- `.scrolling.dimmable.dimmed`: dimmer stand-in never adds this class
- `.markup span.align-center/align-right/float-left/float-right`: never
produced by any renderer, sanitizer strips class attributes
- `.markup ul.no-list`, `.markup ol.no-list`: same as above

---
This PR was written with the help of Claude Opus 4.6

Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.6) <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/css/base.css

@@ -643,10 +643,6 @@ overflow-menu .ui.label {
   color: var(--color-primary-contrast);
 }
 
-.archived-icon {
-  color: var(--color-secondary-dark-2) !important;
-}
-
 .oauth2-authorize-application-box {
   margin-top: 3em !important;
 }
@@ -670,10 +666,6 @@ overflow-menu .ui.label {
   min-width: 50px;
 }
 
-.lines-num span.bottom-line::after {
-  border-bottom: 1px solid var(--color-secondary);
-}
-
 .lines-num span::after {
   content: attr(data-line-number);
   line-height: var(--line-height-code) !important;
@@ -783,11 +775,6 @@ tr.top-line-blame:first-of-type {
   border-top: none; /* merge code lines belonging to the same commit into one block */
 }
 
-.lines-code .bottom-line,
-.lines-commit .bottom-line {
-  border-bottom: 1px solid var(--color-secondary);
-}
-
 .migrate .svg.gitea-git {
   color: var(--color-git);
 }