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/tailwindcss/dist/lib.mjs

@@ -0,0 +1 @@
+import{a,b,c,d,e,f}from"./chunk-L5IEUH3R.mjs";import"./chunk-UWKE2Z6N.mjs";import"./chunk-X4GG3EDV.mjs";export{b as Features,a as Polyfills,e as __unstable__loadDesignSystem,d as compile,c as compileAst,f as default};