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/picomatch/index.js

@@ -0,0 +1,17 @@
+'use strict';
+
+const pico = require('./lib/picomatch');
+const utils = require('./lib/utils');
+
+function picomatch(glob, options, returnState = false) {
+  // default to os.platform()
+  if (options && (options.windows === null || options.windows === undefined)) {
+    // don't mutate the original options object
+    options = { ...options, windows: utils.isWindows() };
+  }
+
+  return pico(glob, options, returnState);
+}
+
+Object.assign(picomatch, pico);
+module.exports = picomatch;