feat: add email sign up

src/composables/useAuth.ts

@@ -0,0 +1,15 @@
+import { authClient } from "@/auth";
+
+export function useAuth() {
+  // Better Auth 提供的 session
+  const session = authClient.useSession();
+
+  const user = computed(() => session.value.data?.user);
+  const isAuthenticated = computed(() => !!session.value.data);
+
+  return {
+    user,
+    session,
+    isAuthenticated,
+  };
+}