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/@babel/template/lib/string.js

@@ -0,0 +1,20 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = stringTemplate;
+var _options = require("./options.js");
+var _parse = require("./parse.js");
+var _populate = require("./populate.js");
+function stringTemplate(formatter, code, opts) {
+  code = formatter.code(code);
+  let metadata;
+  return arg => {
+    const replacements = (0, _options.normalizeReplacements)(arg);
+    if (!metadata) metadata = (0, _parse.default)(formatter, code, opts);
+    return formatter.unwrap((0, _populate.default)(metadata, replacements));
+  };
+}
+
+//# sourceMappingURL=string.js.map