Revert "Rewrite cosmetics and theme preferences (#1292)"

This reverts commit 8704d3acb3.

apps/frontend/src/plugins/1.theme.js

@@ -0,0 +1,27 @@
+export default defineNuxtPlugin(async (nuxtApp) => {
+  await useAuth();
+  await useUser();
+  const themeStore = useTheme();
+  const cosmetics = useCosmetics();
+
+  nuxtApp.hook("app:mounted", () => {
+    if (import.meta.client && themeStore.value.preference === "system") {
+      const colorSchemeQueryList = window.matchMedia("(prefers-color-scheme: light)");
+
+      const setColorScheme = (e) => {
+        if (themeStore.value.preference === "system") {
+          if (e.matches) {
+            updateTheme("light");
+          } else {
+            updateTheme(cosmetics.value.preferredDarkTheme ?? "dark");
+          }
+        }
+      };
+
+      setColorScheme(colorSchemeQueryList);
+      colorSchemeQueryList.addEventListener("change", setColorScheme);
+    }
+  });
+
+  nuxtApp.provide("colorMode", themeStore.value);
+});