style: replace raw colors.css refs with glass tokens from constant.css

Replace @foreground, @primary, @error, @outline, @shadow, @secondary
and their var() equivalents with semantic glass-* tokens across 22 files.
Colors without glass equivalents (@on-primary, @cyan, etc.) left as-is.

src/styles/notification/notification_buttons.css

@@ -34,11 +34,11 @@
 }
 
 #notification-action-buttons button:active {
-  background-color: var(--primary);
+  background-color: @glass-accent;
 }
 
 #notification-action-buttons button:active #button-label {
-  color: var(--shadow);
+  color: @glass-overlay-dark;
 }
 
 .mac-options-button {
@@ -77,8 +77,8 @@ menu.mac-context-menu {
 }
 
 .mac-context-menu menuitem:hover {
-  background-color: var(--primary);
-  color: var(--shadow);
+  background-color: @glass-accent;
+  color: @glass-overlay-dark;
 }
 
 .mac-header-pill {