Tweak repo buttons on mobile and labeled button border-radius (#30503) (#30525)

Backport of https://github.com/go-gitea/gitea/pull/30503 to v1.22, the
only change excluded is the border-radius changes which aren't necessary
on this branch because the button css was not migrated.

Fixes: https://github.com/go-gitea/gitea/issues/30514
Fixes:
https://github.com/go-gitea/gitea/pull/30288#issuecomment-2057466623

- Fix border-radius regression from
https://github.com/go-gitea/gitea/pull/30475
- Fix and simplify hover state
- Move the modal HTML so it does not interfere with the CSS
- Make the star and unwatch text show on mobile. There is still plenty
of space, below is iPhone 12 viewport size

<img width="696" alt="Screenshot 2024-04-15 at 20 34 03"
src="https://github.com/go-gitea/gitea/assets/115237/af90bb00-4671-4973-a255-8eb44ee6ba8d">
<img width="230" alt="Screenshot 2024-04-15 at 20 31 42"
src="https://github.com/go-gitea/gitea/assets/115237/986ef533-7a01-4bb0-8dcd-fd19e4259e84">
<img width="233" alt="Screenshot 2024-04-15 at 20 31 47"
src="https://github.com/go-gitea/gitea/assets/115237/5b825dd8-0ccc-4d56-9d8f-774abb935b68">

web_src/css/modules/button.css

@@ -138,6 +138,13 @@ It needs some tricks to tweak the left/right borders with active state */
   background: var(--color-hover);
 }
 
+.ui.labeled.button > .label:hover {
+  background: var(--color-hover);
+}
+.ui.labeled.button > .button:hover + .label {
+  border-left-color: var(--color-secondary-dark-2);
+}
+
 /* primary */
 
 .ui.primary.labels .label,

web_src/css/modules/label.css

@@ -107,7 +107,7 @@ a.ui.label:hover {
 a.ui.basic.label:hover {
   text-decoration: none;
   color: var(--color-text);
-  border-color: var(--color-light-border);
+  border-color: var(--color-secondary-dark-2);
   background: var(--color-hover);
 }