Adds waitlist feature for booking system

Introduces new waitlist functionality to allow customers to register for unavailable time slots

Includes:
- Waitlist trigger and section in booking interface
- Ability to select preferred time periods
- Date and optional message input
- Success overlay for waitlist submission

Updates salon address in multiple files

wwwroot/poc-booking.html

@@ -864,7 +864,7 @@
         <swp-salon-logo>SB</swp-salon-logo>
         <swp-salon-info>
           <h1>KARINA KNUDSEN®</h1>
-          <p>Hovedgaden 123, København</p>
+          <p>Amager Strandvej 22f, 2300 Kbh S</p>
         </swp-salon-info>
       </swp-salon-header>