scaffold blog_portal vue 3 + pinia + cypress frontend

Mirrors youngstartup/frontend/startups_portal scaffolding:
Vite, Vue 3 (composition API + script setup), TypeScript strict,
Pinia, Vue Router 5, oxlint + eslint + oxfmt, and Cypress with
db:reset / db:seed tasks. Views and the auth store are stubs
filled in by the next branches; routes and the header chrome
are wired so the build passes.

frontend/blog_portal/src/stores/auth.ts

@@ -0,0 +1,37 @@
+import { defineStore } from "pinia";
+import { ref } from "vue";
+
+export interface AuthUser {
+  id: number;
+  email: string;
+  displayName: string;
+  isAdmin: boolean;
+}
+
+export const useAuthStore = defineStore("auth", () => {
+  const user = ref<AuthUser | null>(null);
+  const checked = ref(false);
+  const error = ref<string | null>(null);
+
+  async function fetchMe(): Promise<boolean> {
+    checked.value = true;
+    return false;
+  }
+
+  async function logout(): Promise<void> {
+    user.value = null;
+  }
+
+  function clearError(): void {
+    error.value = null;
+  }
+
+  return {
+    user,
+    checked,
+    error,
+    fetchMe,
+    logout,
+    clearError,
+  };
+});