fix(duckduckgo): ai search assist (#1921)

Author: Koba-gh

styles/duckduckgo/catppuccin.user.less

@@ -152,6 +152,9 @@
     --theme-dc-color-llama-main: @pink !important;
     --theme-dc-color-mixtral-main: @peach !important;
     --theme-dc-color-anchor-sleep: @subtext0 !important;
+    --theme-assist-bg-chat-system: @mantle !important;
+    --theme-assist-gradient-stop: @mantle !important;
+    --sds-color-palette-gray-40: @text !important;
     /* maps */
     --sds-color-background-01: @base !important;
     --sds-color-background-02: @mantle !important;