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/react-router/dist/production/index-react-server-client.d.ts

@@ -0,0 +1,3 @@
+export { b2 as MemoryRouter, b3 as Navigate, b4 as Outlet, b5 as Route, b6 as Router, b7 as RouterProvider, b8 as Routes, aP as UNSAFE_AwaitContextProvider, bA as UNSAFE_WithComponentProps, bE as UNSAFE_WithErrorBoundaryProps, bC as UNSAFE_WithHydrateFallbackProps } from './instrumentation--6Pioq_G.js';
+export { l as BrowserRouter, q as Form, m as HashRouter, n as Link, X as Links, W as Meta, p as NavLink, r as ScrollRestoration, T as StaticRouter, V as StaticRouterProvider, o as unstable_HistoryRouter } from './index-react-server-client-C4tCIird.js';
+import 'react';