feat: implement auth, projects, and frontend foundation

apps/web/src/components/protected-route.tsx

@@ -0,0 +1,19 @@
+import { Navigate, useLocation } from "react-router-dom";
+
+import { useAuth } from "../state/auth";
+
+export const ProtectedRoute = ({ children }: { children: React.ReactNode }) => {
+  const { state } = useAuth();
+  const location = useLocation();
+
+  if (state === "loading") {
+    return <div className="center-screen">Checking session...</div>;
+  }
+
+  if (state === "unauthenticated") {
+    const nextPath = encodeURIComponent(location.pathname);
+    return <Navigate to={`/login?next=${nextPath}`} replace />;
+  }
+
+  return <>{children}</>;
+};