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/App.vue

@@ -0,0 +1,14 @@
+<script setup lang="ts">
+// Root component renders router-managed views.
+</script>
+
+<template>
+  <router-view />
+</template>
+
+<style>
+#app {
+  width: 100%;
+  height: 100%;
+}
+</style>