fix: sanitize API error text display and add time_blockers tests

Add extractErrorMessage helper for JSON error body parsing and apply sanitizeText across all toast displays. Add time_blockers test coverage for new holiday placeholder cleanup and overlapping scenarios.

frontend/src/lib/components/payments/PaymentModal.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
 	import { toast } from 'svelte-sonner';
+	import { extractErrorMessage } from '$lib/utils/toast-safe';
 	import * as Dialog from '$lib/components/ui/dialog';
 	import { Button } from '$lib/components/ui/button';
 	import { Input } from '$lib/components/ui/input';
@@ -241,7 +242,7 @@
 		});
 		if (!res.ok) {
 			const errData = await res.text();
-			throw new Error(errData || 'Failed to apply loyalty discount');
+			throw new Error(extractErrorMessage(errData) || 'Failed to apply loyalty discount');
 		}
 	}
 
@@ -271,7 +272,7 @@
 
 			if (!response.ok) {
 				const errData = await response.text();
-				throw new Error(errData || 'Failed to initiate payment');
+				throw new Error(extractErrorMessage(errData) || 'Failed to initiate payment');
 			}
 
 			const data = await response.json();
@@ -412,7 +413,7 @@
 
 			if (!response.ok) {
 				const errData = await response.text();
-				throw new Error(errData || 'Failed to process payment');
+				throw new Error(extractErrorMessage(errData) || 'Failed to process payment');
 			}
 
 			const data = await response.json();
@@ -539,7 +540,7 @@
 
 			if (!response.ok) {
 				const errData = await response.text();
-				throw new Error(errData || 'Failed to process gift card');
+				throw new Error(extractErrorMessage(errData) || 'Failed to process gift card');
 			}
 
 			const data = await response.json();
@@ -614,7 +615,7 @@
 
 			if (!response.ok) {
 				const errData = await response.text();
-				throw new Error(errData || 'Failed to process saved card payment');
+				throw new Error(extractErrorMessage(errData) || 'Failed to process saved card payment');
 			}
 
 			const data = await response.json();