client(feat): add theme toggle component to navbar for dark/light mod…

client/components/ui/nav-bar.tsx

@@ -8,6 +8,7 @@ import { useState } from "react";
 import Button from "./button";
 import useAuth from "@/lib/hooks/use-auth";
 import { auth } from "@/firebase/firebase";
+import ThemeToggle from "./theme-toggle";
 
 export default function NavBar() {
   const { user } = useAuth();
@@ -52,19 +53,25 @@ export default function NavBar() {
             </Link>
           </li>
         </ul>
-        {user.photoURL ? (
-          <Image
-            className="rounded-full ml-4 cursor-pointer"
-            src={user.photoURL}
-            alt={"user avatar"}
-            width={40}
-            height={40}
-            onClick={() => auth.signOut()}
-          />
-        ) : (
-          // TODO: Set default profile icon
-          <span>No Image</span>
-        )}
+
+        <div className="flex items-center ml-4 gap-3">
+          {/* Theme toggle */}
+          <ThemeToggle />
+
+          {/* user avatar / sign out */}
+          {user.photoURL ? (
+            <Image
+              className="rounded-full cursor-pointer"
+              src={user.photoURL}
+              alt={"user avatar"}
+              width={40}
+              height={40}
+              onClick={() => auth.signOut()}
+            />
+          ) : (
+            <span className="text-white">No Image</span>
+          )}
+        </div>
       </div>
     </nav>
   );

client/components/ui/theme-toggle.tsx

@@ -0,0 +1,62 @@
+"use client";
+
+import React, { useEffect, useState } from "react";
+import { Sun, Moon } from "lucide-react";
+
+/**
+ * ThemeToggle
+ * - toggles "dark" class on document.documentElement
+ * - persists choice in localStorage under "theme"
+ * - only supports "light" and "dark" (no "system" option)
+ */
+export default function ThemeToggle() {
+  const [theme, setTheme] = useState<"light" | "dark">("light");
+  const [mounted, setMounted] = useState(false);
+
+  useEffect(() => {
+    setMounted(true);
+    const saved = localStorage.getItem("theme");
+    if (saved === "light" || saved === "dark") {
+      applyTheme(saved);
+      setTheme(saved);
+    } else {
+      // default to system preference but store as concrete theme
+      const prefersDark = window.matchMedia && window.matchMedia("(prefers-color-scheme: dark)").matches;
+      const initial = prefersDark ? "dark" : "light";
+      applyTheme(initial);
+      setTheme(initial);
+    }
+  }, []);
+
+  const applyTheme = (t: "light" | "dark") => {
+    const root = document.documentElement;
+    if (t === "dark") root.classList.add("dark");
+    else root.classList.remove("dark");
+  };
+
+  const toggle = () => {
+    const next = theme === "dark" ? "light" : "dark";
+    localStorage.setItem("theme", next);
+    applyTheme(next);
+    setTheme(next);
+  };
+
+  if (!mounted) return null;
+
+  const title = theme === "dark" ? "Theme: dark" : "Theme: light";
+
+  return (
+    <button
+      aria-label="Toggle theme"
+      title={title}
+      onClick={toggle}
+      className="inline-flex items-center justify-center p-1 rounded hover:bg-gray-200 dark:hover:bg-gray-700"
+    >
+      {theme === "dark" ? (
+        <Sun className="w-4 h-4 text-yellow-400" />
+      ) : (
+        <Moon className="w-4 h-4 text-gray-700" />
+      )}
+    </button>
+  );
+}