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/parse/_lib/Setter.js

@@ -0,0 +1,57 @@
+import { constructFrom } from "../../constructFrom.js";
+import { transpose } from "../../transpose.js";
+
+const TIMEZONE_UNIT_PRIORITY = 10;
+
+export class Setter {
+  subPriority = 0;
+
+  validate(_utcDate, _options) {
+    return true;
+  }
+}
+
+export class ValueSetter extends Setter {
+  constructor(
+    value,
+
+    validateValue,
+
+    setValue,
+
+    priority,
+    subPriority,
+  ) {
+    super();
+    this.value = value;
+    this.validateValue = validateValue;
+    this.setValue = setValue;
+    this.priority = priority;
+    if (subPriority) {
+      this.subPriority = subPriority;
+    }
+  }
+
+  validate(date, options) {
+    return this.validateValue(date, this.value, options);
+  }
+
+  set(date, flags, options) {
+    return this.setValue(date, flags, this.value, options);
+  }
+}
+
+export class DateTimezoneSetter extends Setter {
+  priority = TIMEZONE_UNIT_PRIORITY;
+  subPriority = -1;
+
+  constructor(context, reference) {
+    super();
+    this.context = context || ((date) => constructFrom(reference, date));
+  }
+
+  set(date, flags) {
+    if (flags.timestampIsSet) return date;
+    return constructFrom(date, transpose(date, this.context));
+  }
+}