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/locale/zh-CN.cjs

@@ -0,0 +1,31 @@
+"use strict";
+exports.zhCN = void 0;
+var _index = require("./zh-CN/_lib/formatDistance.cjs");
+var _index2 = require("./zh-CN/_lib/formatLong.cjs");
+var _index3 = require("./zh-CN/_lib/formatRelative.cjs");
+var _index4 = require("./zh-CN/_lib/localize.cjs");
+var _index5 = require("./zh-CN/_lib/match.cjs");
+
+/**
+ * @category Locales
+ * @summary Chinese Simplified locale.
+ * @language Chinese Simplified
+ * @iso-639-2 zho
+ * @author Changyu Geng [@KingMario](https://github.com/KingMario)
+ * @author Song Shuoyun [@fnlctrl](https://github.com/fnlctrl)
+ * @author sabrinaM [@sabrinamiao](https://github.com/sabrinamiao)
+ * @author Carney Wu [@cubicwork](https://github.com/cubicwork)
+ * @author Terrence Lam [@skyuplam](https://github.com/skyuplam)
+ */
+const zhCN = (exports.zhCN = {
+  code: "zh-CN",
+  formatDistance: _index.formatDistance,
+  formatLong: _index2.formatLong,
+  formatRelative: _index3.formatRelative,
+  localize: _index4.localize,
+  match: _index5.match,
+  options: {
+    weekStartsOn: 1 /* Monday */,
+    firstWeekContainsDate: 4,
+  },
+});