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/tsconfig.tsbuildinfo

@@ -0,0 +1 @@
+{"root":["./src/App.tsx","./src/api.ts","./src/main.tsx","./src/types.ts","./src/vite-env.d.ts","./src/components/AddCalendarUrlModal.tsx","./src/components/CalendarModal.tsx","./src/components/DayView.tsx","./src/components/ErrorBoundary.tsx","./src/components/EventModal.tsx","./src/components/MiniCalendar.tsx","./src/components/Modal.tsx","./src/components/MonthView.tsx","./src/components/WeekView.tsx","./src/context/AuthContext.tsx","./src/context/ThemeContext.tsx","./src/pages/CalendarPage.tsx","./src/pages/ContactsPage.tsx","./src/pages/Login.tsx","./src/pages/Register.tsx","./src/pages/SettingsPage.tsx"],"version":"5.7.3"}