enhance: add permalinks to pull request reviews (#38849) (#39036)

Backport #38849 by @silverwind

1. Make review threads linkable via `#pullrequestreview-<reviewID>`
2. Improve CSS so username and timestamp go colored on hover.
3. CSS cleanup, remove dead rules, nonexistant class name, make
`.suppressed` actually do what it says in the doc above.

<img width="351" height="84" alt="image"
src="https://github.com/user-attachments/assets/6ddf15d4-3d6e-4846-ab82-0ad0b19b372f"
/>

Co-authored-by: silverwind <me@silverwind.io>

web_src/css/base.css

@@ -292,9 +292,7 @@ a.silenced,
 }
 
 a:hover,
-a.suppressed:hover,
 a.muted:hover,
-a.muted:hover [class*="color-text"],
 .muted-links a:hover {
   color: var(--color-primary);
 }