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/minutesToHours.cjs

@@ -0,0 +1,30 @@
+"use strict";
+exports.minutesToHours = minutesToHours;
+var _index = require("./constants.cjs");
+
+/**
+ * @name minutesToHours
+ * @category Conversion Helpers
+ * @summary Convert minutes to hours.
+ *
+ * @description
+ * Convert a number of minutes to a full number of hours.
+ *
+ * @param minutes - The number of minutes to be converted
+ *
+ * @returns The number of minutes converted in hours
+ *
+ * @example
+ * // Convert 140 minutes to hours:
+ * const result = minutesToHours(120)
+ * //=> 2
+ *
+ * @example
+ * // It uses floor rounding:
+ * const result = minutesToHours(179)
+ * //=> 2
+ */
+function minutesToHours(minutes) {
+  const hours = minutes / _index.minutesInHour;
+  return Math.trunc(hours);
+}