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

components/Navbar.tsx

@@ -8,7 +8,7 @@ import { groupOffersByCategory } from "@/lib/angebote";
 import { mainNav, ctaNav, siteConfig } from "@/lib/site";
 import type { Offer } from "@/payload-types";
 
-export function Navbar({ offers }: { offers: Offer[] }) {
+export function Navbar({ offers, customerName }: { offers: Offer[]; customerName?: string | null }) {
   const pathname = usePathname();
   const groups = groupOffersByCategory(offers);
   const [megaOpen, setMegaOpen] = useState(false);
@@ -173,7 +173,13 @@ export function Navbar({ offers }: { offers: Offer[] }) {
           )}
         </nav>
 
-        <div className="hidden lg:block">
+        <div className="hidden items-center gap-5 lg:flex">
+          <Link
+            href={customerName ? "/konto" : "/login"}
+            className="text-[15px] font-medium text-anouma-plum/90 transition-colors hover:text-anouma-mauve-dark"
+          >
+            {customerName ? "Mein Konto" : "Anmelden"}
+          </Link>
           <Link
             href={ctaNav.href}
             className="rounded-full bg-anouma-mauve-dark px-6 py-2.5 text-sm font-medium text-white transition-colors hover:bg-anouma-plum"
@@ -300,6 +306,12 @@ export function Navbar({ offers }: { offers: Offer[] }) {
                   </Link>
                 )
               )}
+              <Link
+                href={customerName ? "/konto" : "/login"}
+                className="border-b border-anouma-taupe/10 py-4 text-lg font-medium text-anouma-plum"
+              >
+                {customerName ? "Mein Konto" : "Anmelden"}
+              </Link>
               <Link
                 href={ctaNav.href}
                 className="mt-6 rounded-full bg-anouma-mauve-dark px-6 py-4 text-center text-base font-medium text-white"