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/rollup/dist/es/rollup.js

@@ -0,0 +1,17 @@
+/*
+  @license
+	Rollup.js v4.59.0
+	Sun, 22 Feb 2026 07:31:53 GMT - commit ae846957f109690a866cc3e4c073613c338d3476
+
+	https://github.com/rollup/rollup
+
+	Released under the MIT License.
+*/
+export { version as VERSION, defineConfig, rollup, watch } from './shared/node-entry.js';
+import './shared/parseAst.js';
+import '../native.js';
+import 'node:path';
+import 'path';
+import 'node:process';
+import 'node:perf_hooks';
+import 'node:fs/promises';