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/isFriday.cjs

@@ -0,0 +1,29 @@
+"use strict";
+exports.isFriday = isFriday;
+var _index = require("./toDate.cjs");
+
+/**
+ * The {@link isFriday} function options.
+ */
+
+/**
+ * @name isFriday
+ * @category Weekday Helpers
+ * @summary Is the given date Friday?
+ *
+ * @description
+ * Is the given date Friday?
+ *
+ * @param date - The date to check
+ * @param options - An object with options
+ *
+ * @returns The date is Friday
+ *
+ * @example
+ * // Is 26 September 2014 Friday?
+ * const result = isFriday(new Date(2014, 8, 26))
+ * //=> true
+ */
+function isFriday(date, options) {
+  return (0, _index.toDate)(date, options?.in).getDay() === 5;
+}