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/payments/PaymentModal.svelte

@@ -4,7 +4,7 @@
 	import { Button } from '$lib/components/ui/button';
 	import { Input } from '$lib/components/ui/input';
 	import { Checkbox } from '$lib/components/ui/checkbox';
-	import type { Booking, BookingService } from '$lib/types/booking';
+	import type { Booking, BookingService, BookingDiscount } from '$lib/types/booking';
 	import { authStore } from '$lib/stores/auth.svelte';
 
 	interface Props {
@@ -91,15 +91,6 @@
 
 	let pollingInterval: ReturnType<typeof setInterval> | null = null;
 
-	let tipPercentages = $derived.by(() => {
-		if (subtotal <= 0) return [];
-		return [
-			{ pct: 10, amount: Math.round(subtotal * 0.1 * 100) / 100 },
-			{ pct: 15, amount: Math.round(subtotal * 0.15 * 100) / 100 },
-			{ pct: 20, amount: Math.round(subtotal * 0.2 * 100) / 100 }
-		];
-	});
-
 	function selectTipPercent(percent: number) {
 		selectedTipPercent = percent;
 		customTipAmount = '';
@@ -135,16 +126,27 @@
 	}
 
 	let subtotal = $derived((booking.services ?? []).reduce((sum, s) => sum + getServicePrice(s), 0));
+	let discountSum = $derived((booking.discounts ?? []).reduce((sum, d) => sum + d.discount_amount, 0));
+	let netTotal = $derived(Math.max(0, subtotal - discountSum));
+
+	let tipPercentages = $derived.by(() => {
+		if (netTotal <= 0) return [];
+		return [
+			{ pct: 10, amount: Math.round(netTotal * 0.1 * 100) / 100 },
+			{ pct: 15, amount: Math.round(netTotal * 0.15 * 100) / 100 },
+			{ pct: 20, amount: Math.round(netTotal * 0.2 * 100) / 100 }
+		];
+	});
 
 	let tipMultiplier = $derived(
 		selectedTipPercent !== null
 			? 1 + selectedTipPercent / 100
 			: customTipAmount && parseFloat(customTipAmount) > 0
-				? 1 + parseFloat(customTipAmount) / subtotal
+				? 1 + parseFloat(customTipAmount) / netTotal
 				: 1
 	);
 
-	let totalWithTip = $derived(tipEnabled ? subtotal * tipMultiplier : subtotal);
+	let totalWithTip = $derived(tipEnabled ? netTotal * tipMultiplier : netTotal);
 	let tipDisplay = $derived(
 		selectedTipPercent !== null
 			? `${selectedTipPercent}%`
@@ -153,7 +155,7 @@
 				: ''
 	);
 
-	let totalDue = $derived(tipEnabled ? totalWithTip : subtotal);
+	let totalDue = $derived(tipEnabled ? totalWithTip : netTotal);
 
 	function formatCurrency(value: number): string {
 		return new Intl.NumberFormat('en-GB', {
@@ -469,9 +471,50 @@
 					</div>
 				</div>
 
-				<div class="flex justify-between rounded-md border border-gray-200 bg-white p-4">
+				{#if booking.discounts && booking.discounts.length > 0}
+					<div class="rounded-md border border-fuchsia-100 bg-fuchsia-50/40 p-4">
+						<div class="mb-3 flex items-center justify-between">
+							<div class="text-sm font-semibold text-fuchsia-800 flex items-center gap-1.5">
+								<svg class="h-4 w-4 text-fuchsia-600" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+									<path d="M20.59 13.41l-7.17 7.17a2 2 0 0 1-2.83 0L2 12V2h10l8.59 8.59a2 2 0 0 1 0 2.82z"></path>
+									<line x1="7" y1="7" x2="7.01" y2="7"></line>
+								</svg>
+								Applied Discounts
+							</div>
+							<span class="rounded-full bg-fuchsia-100 px-2 py-0.5 text-xs font-semibold text-fuchsia-700">
+								{((discountSum / subtotal) * 100).toFixed(0)}% Off Total
+							</span>
+						</div>
+						<div class="space-y-2 text-sm">
+							{#each booking.discounts as d}
+								<div class="flex items-center justify-between text-gray-600">
+									<div class="flex items-center gap-1.5">
+										<span class="h-1.5 w-1.5 rounded-full bg-fuchsia-500"></span>
+										<span>
+											{#if d.discount_source === 'loyalty'}
+												Loyalty Stamp Card (10% Off)
+											{:else if d.campaign_name}
+												{d.campaign_name}
+											{:else}
+												Promo Campaign ({d.discount_percent}% Off)
+											{/if}
+										</span>
+									</div>
+									<span class="font-medium text-fuchsia-600">-{formatCurrency(d.discount_amount)}</span>
+								</div>
+							{/each}
+						</div>
+					</div>
+				{/if}
+
+				<div class="flex justify-between items-center rounded-md border border-gray-200 bg-white p-4">
 					<span class="text-base font-semibold text-gray-700">Total</span>
-					<span class="text-xl font-bold text-gray-900">{formatCurrency(subtotal)}</span>
+					<div class="flex items-baseline gap-2.5">
+						{#if discountSum > 0.01}
+							<span class="text-sm font-medium text-gray-400 line-through">{formatCurrency(subtotal)}</span>
+						{/if}
+						<span class="text-xl font-bold text-gray-900">{formatCurrency(totalDue)}</span>
+					</div>
 				</div>
 
 				{#if tipEnabled}