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/getDay.d.ts

@@ -0,0 +1,27 @@
+import type { ContextOptions, DateArg } from "./types.js";
+/**
+ * The {@link getDay} function options.
+ */
+export interface GetDayOptions extends ContextOptions<Date> {}
+/**
+ * @name getDay
+ * @category Weekday Helpers
+ * @summary Get the day of the week of the given date.
+ *
+ * @description
+ * Get the day of the week of the given date.
+ *
+ * @param date - The given date
+ * @param options - The options
+ *
+ * @returns The day of week, 0 represents Sunday
+ *
+ * @example
+ * // Which day of the week is 29 February 2012?
+ * const result = getDay(new Date(2012, 1, 29))
+ * //=> 3
+ */
+export declare function getDay(
+  date: DateArg<Date> & {},
+  options?: GetDayOptions | undefined,
+): number;