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/date-fns/parse/_lib/parsers/ISOTimezoneParser.cjs

@@ -0,0 +1,57 @@
+"use strict";
+exports.ISOTimezoneParser = void 0;
+var _index = require("../../../constructFrom.cjs");
+var _index2 = require("../../../_lib/getTimezoneOffsetInMilliseconds.cjs");
+var _constants = require("../constants.cjs");
+var _Parser = require("../Parser.cjs");
+
+var _utils = require("../utils.cjs");
+
+// Timezone (ISO-8601)
+class ISOTimezoneParser extends _Parser.Parser {
+  priority = 10;
+
+  parse(dateString, token) {
+    switch (token) {
+      case "x":
+        return (0, _utils.parseTimezonePattern)(
+          _constants.timezonePatterns.basicOptionalMinutes,
+          dateString,
+        );
+      case "xx":
+        return (0, _utils.parseTimezonePattern)(
+          _constants.timezonePatterns.basic,
+          dateString,
+        );
+      case "xxxx":
+        return (0, _utils.parseTimezonePattern)(
+          _constants.timezonePatterns.basicOptionalSeconds,
+          dateString,
+        );
+      case "xxxxx":
+        return (0, _utils.parseTimezonePattern)(
+          _constants.timezonePatterns.extendedOptionalSeconds,
+          dateString,
+        );
+      case "xxx":
+      default:
+        return (0, _utils.parseTimezonePattern)(
+          _constants.timezonePatterns.extended,
+          dateString,
+        );
+    }
+  }
+
+  set(date, flags, value) {
+    if (flags.timestampIsSet) return date;
+    return (0, _index.constructFrom)(
+      date,
+      date.getTime() -
+        (0, _index2.getTimezoneOffsetInMilliseconds)(date) -
+        value,
+    );
+  }
+
+  incompatibleTokens = ["t", "T", "X"];
+}
+exports.ISOTimezoneParser = ISOTimezoneParser;