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/jiti/lib/jiti.mjs

@@ -0,0 +1,29 @@
+import { createRequire } from "node:module";
+import _createJiti from "../dist/jiti.cjs";
+
+function onError(err) {
+  throw err; /* ↓ Check stack trace ↓ */
+}
+
+const nativeImport = (id) => import(id);
+
+let _transform;
+function lazyTransform(...args) {
+  if (!_transform) {
+    _transform = createRequire(import.meta.url)("../dist/babel.cjs");
+  }
+  return _transform(...args);
+}
+
+export function createJiti(id, opts = {}) {
+  if (!opts.transform) {
+    opts = { ...opts, transform: lazyTransform };
+  }
+  return _createJiti(id, opts, {
+    onError,
+    nativeImport,
+    createRequire,
+  });
+}
+
+export default createJiti;