Add OpenAPI docs, frontend, migrations, and API updates

- OpenAPI: add missing endpoints (add-from-url, subscriptions, public availability)
- OpenAPI: CalendarSubscription schema, Subscriptions tag
- Frontend app
- Migrations: count_for_availability, subscriptions_sync, user_preferences, calendar_settings
- Config, rate limit, auth, calendar, booking, ICS, availability, user service updates

Made-with: Cursor

frontend/node_modules/vite/README.md

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+# vite ⚡
+
+> Next Generation Frontend Tooling
+
+- 💡 Instant Server Start
+- ⚡️ Lightning Fast HMR
+- 🛠️ Rich Features
+- 📦 Optimized Build
+- 🔩 Universal Plugin Interface
+- 🔑 Fully Typed APIs
+
+Vite (French word for "fast", pronounced `/vit/`) is a new breed of frontend build tool that significantly improves the frontend development experience. It consists of two major parts:
+
+- A dev server that serves your source files over [native ES modules](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules), with [rich built-in features](https://vite.dev/guide/features.html) and astonishingly fast [Hot Module Replacement (HMR)](https://vite.dev/guide/features.html#hot-module-replacement).
+
+- A [build command](https://vite.dev/guide/build.html) that bundles your code with [Rollup](https://rollupjs.org), pre-configured to output highly optimized static assets for production.
+
+In addition, Vite is highly extensible via its [Plugin API](https://vite.dev/guide/api-plugin.html) and [JavaScript API](https://vite.dev/guide/api-javascript.html) with full typing support.
+
+[Read the Docs to Learn More](https://vite.dev).