fix: booking duration calculation, tip page auth, and UI polish across frontend

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

frontend/src/lib/components/admin/WeeklySchedule.svelte

@@ -7,6 +7,7 @@
 	import { Button } from '$lib/components/ui/button';
 	import * as Card from '$lib/components/ui/card';
 	import { Input } from '$lib/components/ui/input';
+	import { Checkbox } from '$lib/components/ui/checkbox';
 	import * as Modal from '$lib/components/ui/dialog';
 	import * as AlertDialog from '$lib/components/ui/alert-dialog';
 	import { Skeleton } from '$lib/components/ui/skeleton';
@@ -475,11 +476,7 @@
 							<tr class="border-t">
 								<td class="py-2 text-sm">{weekdayLabel(row.weekday)}</td>
 								<td class="py-2">
-									<input
-										type="checkbox"
-										bind:checked={row.is_open}
-										class="h-4 w-4 rounded border-gray-300 bg-gray-100 text-primary focus:ring-primary"
-									/>
+									<Checkbox bind:checked={row.is_open} />
 								</td>
 								<td class="py-2">
 									<Input