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/getDate.cjs

@@ -0,0 +1,29 @@
+"use strict";
+exports.getDate = getDate;
+var _index = require("./toDate.cjs");
+
+/**
+ * The {@link getDate} function options.
+ */
+
+/**
+ * @name getDate
+ * @category Day Helpers
+ * @summary Get the day of the month of the given date.
+ *
+ * @description
+ * Get the day of the month of the given date.
+ *
+ * @param date - The given date
+ * @param options - An object with options.
+ *
+ * @returns The day of month
+ *
+ * @example
+ * // Which day of the month is 29 February 2012?
+ * const result = getDate(new Date(2012, 1, 29))
+ * //=> 29
+ */
+function getDate(date, options) {
+  return (0, _index.toDate)(date, options?.in).getDate();
+}