Dark/light mode added + switcher

frontend/src/hooks/useTheme.js

@@ -0,0 +1,16 @@
+import { useEffect, useState } from "react";
+import { getInitialTheme, applyTheme, toggleTheme } from "../utils/theme";
+
+export function useTheme() {
+    const [theme, setTheme] = useState(getInitialTheme);
+
+    useEffect(() => {
+        applyTheme(theme);
+    }, [theme]);
+
+    const handleToggle = () => {
+        setTheme((prev) => toggleTheme(prev));
+    };
+
+    return { theme, toggleTheme: handleToggle };
+}