feat(loyalty-discount): implement loyalty and discount system

- Add discount campaign management and validation logic
- Update booking handlers with discount application flow
- Add customer relationship endpoints for loyalty tracking
- Update frontend modals (booking, approval, payment, reschedule)
- Add DiscountsManagement and loyalty reference documentation
- Update dev scripts and database init for discount tables
- Clean up completed plan files

frontend/src/lib/components/account/EditRequestModal.svelte

@@ -720,7 +720,7 @@
 
 <Modal.Root bind:open>
 	<Modal.Content
-		class="max-h-[90vh] max-w-[calc(100%-2rem)] overflow-y-auto sm:max-w-md md:max-w-3xl"
+		class="!z-[70] max-h-[90vh] max-w-[calc(100%-2rem)] overflow-y-auto sm:max-w-md md:max-w-3xl"
 	>
 		<Modal.Header>
 			<div class="flex items-center justify-between">