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/tsconfig.app.json

@@ -0,0 +1,18 @@
+{
+  "extends": "@vue/tsconfig/tsconfig.dom.json",
+  "include": ["env.d.ts", "src/**/*", "src/**/*.vue"],
+  "exclude": ["src/**/__tests__/*"],
+  "compilerOptions": {
+    // Extra safety for array and object lookups, but may have false positives.
+    "noUncheckedIndexedAccess": true,
+
+    // Path mapping for cleaner imports.
+    "paths": {
+      "@/*": ["./src/*"]
+    },
+
+    // `vue-tsc --build` produces a .tsbuildinfo file for incremental type-checking.
+    // Specified here to keep it out of the root directory.
+    "tsBuildInfoFile": "./node_modules/.tmp/tsconfig.app.tsbuildinfo"
+  }
+}