feat: add support for light mode (#438)

* feat: add support for light mode

* refactor: use shadcn theme toggle

* fix: fix sonner

frontend/src/components/layout/layout.tsx

@@ -3,6 +3,7 @@ import { LanguageSelector } from "../language/language";
 import { Outlet } from "react-router";
 import { useCallback, useEffect, useState } from "react";
 import { DomainWarning } from "../domain-warning/domain-warning";
+import { ThemeToggle } from "../theme-toggle/theme-toggle";
 
 const BaseLayout = ({ children }: { children: React.ReactNode }) => {
   const { backgroundImage, title } = useAppContext();
@@ -20,7 +21,10 @@ const BaseLayout = ({ children }: { children: React.ReactNode }) => {
         backgroundPosition: "center",
       }}
     >
-      <LanguageSelector />
+      <div className="absolute top-5 right-5 flex flex-row gap-2">
+        <ThemeToggle />
+        <LanguageSelector />
+      </div>
       {children}
     </div>
   );