Add calendar-based booking system: accounts, availability, admin calendar

- Customer accounts (separate auth collection) with /konto area
- Availability + AvailabilityOverrides collections driving real slot calculation
- BookingRequests with race-safe confirmation (Postgres advisory lock + transaction)
- Booking emails (request received, admin notify, confirmed, rejected, alternative proposed/accepted, cancelled)
- Confirmed online bookings auto-create a private linked video-call Event
- Custom Payload admin calendar view (month grid + day schedule)
- Wired booking widget into offer pages and /termin-buchen

payload.config.ts

@@ -38,6 +38,17 @@ export default buildConfig({
     meta: {
       titleSuffix: "— Anouma Admin",
     },
+    components: {
+      afterNavLinks: ["/components/admin/CalendarNavLink#CalendarNavLink"],
+      views: {
+        kalender: {
+          Component: "/components/admin/AdminCalendarView#AdminCalendarView",
+          path: "/kalender",
+          exact: true,
+          meta: { title: "Kalender" },
+        },
+      },
+    },
   },
   collections: [
     Users,