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/date-fns/getDefaultOptions.js

@@ -0,0 +1,32 @@
+import { getDefaultOptions as getInternalDefaultOptions } from "./_lib/defaultOptions.js";
+
+/**
+ * @name getDefaultOptions
+ * @category Common Helpers
+ * @summary Get default options.
+ * @pure false
+ *
+ * @description
+ * Returns an object that contains defaults for
+ * `options.locale`, `options.weekStartsOn` and `options.firstWeekContainsDate`
+ * arguments for all functions.
+ *
+ * You can change these with [setDefaultOptions](https://date-fns.org/docs/setDefaultOptions).
+ *
+ * @returns The default options
+ *
+ * @example
+ * const result = getDefaultOptions()
+ * //=> {}
+ *
+ * @example
+ * setDefaultOptions({ weekStarsOn: 1, firstWeekContainsDate: 4 })
+ * const result = getDefaultOptions()
+ * //=> { weekStarsOn: 1, firstWeekContainsDate: 4 }
+ */
+export function getDefaultOptions() {
+  return Object.assign({}, getInternalDefaultOptions());
+}
+
+// Fallback for modularized imports:
+export default getDefaultOptions;