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/source-map-js/source-map.js

@@ -0,0 +1,8 @@
+/*
+ * Copyright 2009-2011 Mozilla Foundation and contributors
+ * Licensed under the New BSD license. See LICENSE.txt or:
+ * http://opensource.org/licenses/BSD-3-Clause
+ */
+exports.SourceMapGenerator = require('./lib/source-map-generator').SourceMapGenerator;
+exports.SourceMapConsumer = require('./lib/source-map-consumer').SourceMapConsumer;
+exports.SourceNode = require('./lib/source-node').SourceNode;