feat(theme): add dark mode with next-themes and settings toggle

components/theme-sync.tsx

@@ -0,0 +1,17 @@
+"use client"
+
+import { useAuthStore } from "@/store/auth"
+import { useTheme } from "next-themes"
+import { useEffect } from "react"
+
+export function ThemeSyncEffect() {
+  const { setTheme } = useTheme()
+  const isAuthenticated = useAuthStore((s) => s.isAuthenticated)
+  const themePreference = useAuthStore((s) => s.themePreference)
+
+  useEffect(() => {
+    setTheme(themePreference)
+  }, [isAuthenticated, themePreference, setTheme])
+
+  return null
+}