feat: add Sign In button to Navbar for improved user navigation

Author: adity1raut

client/src/App.jsx

@@ -5,7 +5,6 @@ import { AuthProvider, useAuth } from "./context/AuthContext";
 import ProtectedRoutes from "./routes/ProtectedRoutes";
 import PublicRoutes from "./routes/PublicRoutes";
 import ThemeApplier from "./theme/ThemeApplier";
-import Mainpage from "./pages/Mainpage";
 
 function AppRoutes() {
   const { user } = useAuth();

client/src/components/Navbar.jsx

@@ -594,6 +594,18 @@ function Navbar({ showBack }) {
               Home
             </button>
 
+            <button
+              onClick={() => navigate("/signin")}
+              className="hidden sm:flex px-4 py-2 rounded-xl text-sm font-semibold 
+                         border border-[var(--accent)]/50 text-[var(--accent)] glass
+                         hover:border-[var(--accent)] hover:bg-[var(--accent)]/15
+                         hover:shadow-[0_4px_16px_-4px_var(--accent)]
+                         transition-all duration-300 cursor-pointer active:scale-95
+                         items-center gap-2"
+            >
+              Sign In
+            </button>
+
             <button
               onClick={() => navigate("/signup")}
               className="px-4 py-2 rounded-xl text-sm font-bold border-none