Project board improvements (#15429)

* Project board improvements

- Fix link colors
- Extract CSS to own file
- Various minor tweaks to make it look better

Fixes: https://github.com/go-gitea/gitea/issues/15424
Fixes: https://github.com/go-gitea/gitea/issues/15506
Fixes: https://github.com/go-gitea/gitea/pull/15511

* fix squashed cards on small view area

* more css fixes, add second row from issue list

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

web_src/less/index.less

@@ -8,6 +8,7 @@
 @import "./features/heatmap.less";
 @import "./features/imagediff.less";
 @import "./features/codeeditor.less";
+@import "./features/projects.less";
 @import "./markdown/mermaid.less";
 
 @import "./chroma/base.less";