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/startOfToday.js

@@ -0,0 +1,32 @@
+import { startOfDay } from "./startOfDay.js";
+
+/**
+ * The {@link startOfToday} function options.
+ */
+
+/**
+ * @name startOfToday
+ * @category Day Helpers
+ * @summary Return the start of today.
+ * @pure false
+ *
+ * @description
+ * Return the start of today.
+ *
+ * @typeParam ContextDate - The `Date` type of the context function.
+ *
+ * @param options - An object with options
+ *
+ * @returns The start of today
+ *
+ * @example
+ * // If today is 6 October 2014:
+ * const result = startOfToday()
+ * //=> Mon Oct 6 2014 00:00:00
+ */
+export function startOfToday(options) {
+  return startOfDay(Date.now(), options);
+}
+
+// Fallback for modularized imports:
+export default startOfToday;