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/getOverlappingDaysInIntervals.d.ts

@@ -0,0 +1,40 @@
+import type { Interval } from "./types.js";
+/**
+ * @name getOverlappingDaysInIntervals
+ * @category Interval Helpers
+ * @summary Get the number of days that overlap in two time intervals
+ *
+ * @description
+ * Get the number of days that overlap in two time intervals. It uses the time
+ * between dates to calculate the number of days, rounding it up to include
+ * partial days.
+ *
+ * Two equal 0-length intervals will result in 0. Two equal 1ms intervals will
+ * result in 1.
+ *
+ * @param intervalLeft - The first interval to compare.
+ * @param intervalRight - The second interval to compare.
+ * @param options - An object with options
+ *
+ * @returns The number of days that overlap in two time intervals
+ *
+ * @example
+ * // For overlapping time intervals adds 1 for each started overlapping day:
+ * getOverlappingDaysInIntervals(
+ *   { start: new Date(2014, 0, 10), end: new Date(2014, 0, 20) },
+ *   { start: new Date(2014, 0, 17), end: new Date(2014, 0, 21) }
+ * )
+ * //=> 3
+ *
+ * @example
+ * // For non-overlapping time intervals returns 0:
+ * getOverlappingDaysInIntervals(
+ *   { start: new Date(2014, 0, 10), end: new Date(2014, 0, 20) },
+ *   { start: new Date(2014, 0, 21), end: new Date(2014, 0, 22) }
+ * )
+ * //=> 0
+ */
+export declare function getOverlappingDaysInIntervals(
+  intervalLeft: Interval,
+  intervalRight: Interval,
+): number;