feat(web): wire auth pages with BetterAuth and route guards (#83)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/src/components/auth-guard.tsx

@@ -0,0 +1,34 @@
+'use client';
+
+import { useRouter } from 'next/navigation';
+import { useEffect } from 'react';
+import { useSession } from '@/lib/auth-client';
+
+interface AuthGuardProps {
+  children: React.ReactNode;
+}
+
+export function AuthGuard({ children }: AuthGuardProps): React.ReactElement | null {
+  const { data: session, isPending } = useSession();
+  const router = useRouter();
+
+  useEffect(() => {
+    if (!isPending && !session) {
+      router.replace('/login');
+    }
+  }, [isPending, session, router]);
+
+  if (isPending) {
+    return (
+      <div className="flex min-h-screen items-center justify-center">
+        <div className="text-sm text-text-muted">Loading...</div>
+      </div>
+    );
+  }
+
+  if (!session) {
+    return null;
+  }
+
+  return <>{children}</>;
+}

apps/web/src/components/guest-guard.tsx

@@ -0,0 +1,35 @@
+'use client';
+
+import { useRouter } from 'next/navigation';
+import { useEffect } from 'react';
+import { useSession } from '@/lib/auth-client';
+
+interface GuestGuardProps {
+  children: React.ReactNode;
+}
+
+/** Redirects authenticated users away from auth pages. */
+export function GuestGuard({ children }: GuestGuardProps): React.ReactElement | null {
+  const { data: session, isPending } = useSession();
+  const router = useRouter();
+
+  useEffect(() => {
+    if (!isPending && session) {
+      router.replace('/chat');
+    }
+  }, [isPending, session, router]);
+
+  if (isPending) {
+    return (
+      <div className="flex min-h-screen items-center justify-center">
+        <div className="text-sm text-text-muted">Loading...</div>
+      </div>
+    );
+  }
+
+  if (session) {
+    return null;
+  }
+
+  return <>{children}</>;
+}

apps/web/src/components/layout/topbar.tsx

@@ -1,9 +1,16 @@
 'use client';
 
+import { useRouter } from 'next/navigation';
 import { useSession, signOut } from '@/lib/auth-client';
 
 export function Topbar(): React.ReactElement {
   const { data: session } = useSession();
+  const router = useRouter();
+
+  async function handleSignOut(): Promise<void> {
+    await signOut();
+    router.replace('/login');
+  }
 
   return (
     <header className="sticky top-0 z-20 flex h-14 items-center justify-between border-b border-surface-border bg-surface-card/80 px-6 backdrop-blur-sm">
@@ -17,7 +24,7 @@ export function Topbar(): React.ReactElement {
             </span>
             <button
               type="button"
-              onClick={() => signOut()}
+              onClick={handleSignOut}
               className="rounded-md px-3 py-1.5 text-sm text-text-muted transition-colors hover:bg-surface-elevated hover:text-text-primary"
             >
               Sign out