feat(app): initialize uni-app with routing, stores, and infrastructure

- Vue 3 + TypeScript + Pinia + SCSS
- 3-tab navigation (home, booking, profile) + 11 sub-pages
- HTTP client with JWT auth, request interceptors
- Pinia stores: user (auth, profile, memberships), studio, booking
- Utility functions: price formatting, date helpers
- WeChat login helper
- All pages as stubs ready for implementation

packages/app/src/App.vue

@@ -0,0 +1,17 @@
+<script setup lang="ts">
+import { onLaunch } from '@dcloudio/uni-app'
+import { useUserStore } from './stores/user'
+
+onLaunch(() => {
+  console.log('App Launch')
+  const userStore = useUserStore()
+  userStore.checkAuth()
+})
+</script>
+
+<style>
+page {
+  background-color: #f5f5f5;
+  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+}
+</style>