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/_lib/test.js

@@ -0,0 +1,51 @@
+import { afterEach, beforeEach } from "./test/vitest";
+import { addLeadingZeros } from "./addLeadingZeros.js";
+import { setDefaultOptions } from "./defaultOptions.js";
+import sinon from "./test/sinon";
+
+export function assertType(_value) {}
+
+export function resetDefaultOptions() {
+  setDefaultOptions({});
+}
+
+// This makes sure we create the consistent offsets across timezones, no matter where these tests are ran.
+export function generateOffset(originalDate) {
+  // Add the timezone.
+  let offset = "";
+  const tzOffset = originalDate.getTimezoneOffset();
+
+  if (tzOffset !== 0) {
+    const absoluteOffset = Math.abs(tzOffset);
+    const hourOffset = addLeadingZeros(Math.trunc(absoluteOffset / 60), 2);
+    const minuteOffset = addLeadingZeros(absoluteOffset % 60, 2);
+    // If less than 0, the sign is +, because it is ahead of time.
+    const sign = tzOffset < 0 ? "+" : "-";
+
+    offset = `${sign}${hourOffset}:${minuteOffset}`;
+  } else {
+    offset = "Z";
+  }
+
+  return offset;
+}
+
+export function fakeDate(date) {
+  let clock;
+
+  function fakeNow(date) {
+    clock?.restore();
+    clock = sinon.useFakeTimers(+date);
+  }
+
+  beforeEach(() => {
+    fakeNow(+date);
+  });
+
+  afterEach(() => {
+    clock?.restore();
+    clock = undefined;
+  });
+
+  return { fakeNow };
+}