Remove fomantic transition module (#26469)

Removes all dropdown and dimmer animations. Works everywhere as far as I
can tell, but need to give this thorough testing. Removes around 70kb
JS/CSS.

Note, I'm not 100% sure regarding the various callbacks, those will need
more investigation, but it appears to work nonetheless.

Fixes: #15709

web_src/css/base.css

@@ -225,7 +225,7 @@
   --color-button: #fafafa;
   --color-code-bg: #ffffff;
   --color-code-sidebar-bg: #f5f5f5;
-  --color-shadow: #00000030;
+  --color-shadow: #00000026;
   --color-secondary-bg: #f4f4f4;
   --color-expand-button: #d8efff;
   --color-placeholder-text: #aaa;
@@ -248,6 +248,7 @@
   --color-accent: var(--color-primary-light-1);
   --color-small-accent: var(--color-primary-light-6);
   --color-active-line: #fffbdd;
+  --color-overlay-backdrop: #080808c0;
   accent-color: var(--color-accent);
   color-scheme: light;
 }
@@ -705,6 +706,16 @@ a.label,
   background: var(--color-active) !important;
 }
 
+/* styles from removed fomantic transition module */
+.hidden.transition {
+  visibility: hidden;
+  display: none;
+}
+.visible.transition {
+  display: block !important;
+  visibility: visible !important;
+}
+
 .ui.message {
   background: var(--color-box-body);
   color: var(--color-text);
@@ -796,7 +807,7 @@ a.label,
 .ui.selection.active.dropdown:hover,
 .ui.selection.active.dropdown .menu,
 .ui.selection.active.dropdown:hover .menu {
-  border-color: var(--color-primary-light-2);
+  border-color: var(--color-primary);
 }
 
 .ui.selection.dropdown .menu {
@@ -1186,6 +1197,20 @@ img.ui.avatar,
   box-shadow: none;
 }
 
+.ui.dropdown .menu,
+.ui.upward.dropdown > .menu,
+.ui.menu .dropdown.item .menu,
+.ui.selection.active.dropdown .menu,
+.ui.upward.selection.dropdown .menu,
+.ui.selection.active.dropdown:hover .menu,
+.ui.upward.active.selection.dropdown:hover .menu {
+  box-shadow: 0 6px 18px var(--color-shadow);
+}
+
+.ui.dimmer {
+  background: var(--color-overlay-backdrop);
+}
+
 /* Override semantic selector '.ui.menu:not(.vertical) .item > .button' */
 /* This fixes the commit graph button on the commits page */
 /* modal svg icons, copied from fomantic except width and height */

web_src/css/modules/animations.css

@@ -105,3 +105,9 @@ code.language-math.is-loading::after {
 .pulse {
   animation: pulse 2s linear;
 }
+
+.ui.modal {
+  animation-name: fadein;
+  animation-duration: 300ms;
+  animation-timing-function: ease-in-out;
+}

web_src/css/themes/theme-arc-green.css

@@ -233,6 +233,7 @@
   --color-accent: var(--color-primary-light-1);
   --color-small-accent: var(--color-primary-light-5);
   --color-active-line: #534d1b;
+  --color-overlay-backdrop: #080808c0;
   accent-color: var(--color-accent);
   color-scheme: dark;
 }