chore: migrate to pnpm workspaces monorepo with Turborepo

- Restructure directories: apps/api, apps/admin, apps/website
- Add root pnpm-workspace.yaml, turbo.json, .prettierrc, .gitignore
- Rename packages to @inkreach/api, @inkreach/admin, @inkreach/website
- Add shared packages: packages/tsconfig, packages/shared-types
- Add pnpm.onlyBuiltDependencies for native builds
- Update docs: README.md, structs.md
- All three projects build successfully

apps/admin/src/main.ts

@@ -0,0 +1,15 @@
+import { createApp } from 'vue'
+import { createPinia } from 'pinia'
+import ElementPlus from 'element-plus'
+import 'element-plus/dist/index.css'
+import './style.css'
+import App from './App.vue'
+import router from './router'
+
+const app = createApp(App)
+
+app.use(createPinia())
+app.use(router)
+app.use(ElementPlus)
+
+app.mount('#app')