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/differenceInCalendarISOWeeks.d.ts

@@ -0,0 +1,35 @@
+import type { ContextOptions, DateArg } from "./types.js";
+/**
+ * The {@link differenceInCalendarISOWeeks} function options.
+ */
+export interface DifferenceInCalendarISOWeeksOptions
+  extends ContextOptions<Date> {}
+/**
+ * @name differenceInCalendarISOWeeks
+ * @category ISO Week Helpers
+ * @summary Get the number of calendar ISO weeks between the given dates.
+ *
+ * @description
+ * Get the number of calendar ISO weeks between the given dates.
+ *
+ * ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date
+ *
+ * @param laterDate - The later date
+ * @param earlierDate - The earlier date
+ * @param options - An object with options
+ *
+ * @returns The number of calendar ISO weeks
+ *
+ * @example
+ * // How many calendar ISO weeks are between 6 July 2014 and 21 July 2014?
+ * const result = differenceInCalendarISOWeeks(
+ *   new Date(2014, 6, 21),
+ *   new Date(2014, 6, 6),
+ * );
+ * //=> 3
+ */
+export declare function differenceInCalendarISOWeeks(
+  laterDate: DateArg<Date> & {},
+  earlierDate: DateArg<Date> & {},
+  options?: DifferenceInCalendarISOWeeksOptions | undefined,
+): number;