Fix colour regressions (#11273)

* Fix color contrast of notice events

Fixes https://github.com/vector-im/element-web/issues/25808

* Restore alert color for highlighted events

Fixes https://github.com/vector-im/element-web/issues/25788

* Fix quote border for highlighted events

Fixes https://github.com/vector-im/element-web/issues/25811

* Fix media background mixing with event highlighted

Fixes https://github.com/vector-im/element-web/issues/25812

res/themes/light/css/_light.pcss

@@ -103,7 +103,7 @@ $muted-fg-color: #61708b;
 $light-fg-color: #747474;
 $focus-bg-color: $preview-widget-bar-color;
 $info-plinth-bg-color: #f7f7f7;
-$event-selected-color: #f6f7f8;
+$event-selected-color: var(--cpd-color-bg-subtle-secondary);
 $topleftmenu-color: #212121;
 $roomtopic-color: #9e9e9e;
 $spacePanel-bg-color: rgba(232, 232, 232, 0.77);
@@ -115,7 +115,7 @@ $header-panel-text-primary-color: #91a1c0;
 
 /* Blockquote */
 /* ******************** */
-$blockquote-bar-color: $focus-bg-color;
+$blockquote-bar-color: var(--cpd-color-border-interactive-primary);
 /* ******************** */
 
 /* Tooltip */