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/SecondParser.cjs

@@ -0,0 +1,36 @@
+"use strict";
+exports.SecondParser = void 0;
+var _constants = require("../constants.cjs");
+var _Parser = require("../Parser.cjs");
+
+var _utils = require("../utils.cjs");
+
+class SecondParser extends _Parser.Parser {
+  priority = 50;
+
+  parse(dateString, token, match) {
+    switch (token) {
+      case "s":
+        return (0, _utils.parseNumericPattern)(
+          _constants.numericPatterns.second,
+          dateString,
+        );
+      case "so":
+        return match.ordinalNumber(dateString, { unit: "second" });
+      default:
+        return (0, _utils.parseNDigits)(token.length, dateString);
+    }
+  }
+
+  validate(_date, value) {
+    return value >= 0 && value <= 59;
+  }
+
+  set(date, _flags, value) {
+    date.setSeconds(value, 0);
+    return date;
+  }
+
+  incompatibleTokens = ["t", "T"];
+}
+exports.SecondParser = SecondParser;