feat(frontend): add custom services management UI components

Add CustomServicesManagement component for CRUD operations on custom services. Update BookingCreateModal, WalkInCreateModal, and BookingsCard to support custom service selection. Minor improvements to ServicesManagement and ImageUpload.

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

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

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

@@ -23,6 +23,8 @@
 		created_by?: string;
 	};
 
+	const durationOptions = Array.from({ length: 32 }, (_, i) => (i + 1) * 15);
+
 	let services = $state<Service[]>([]);
 	let newService = $state<
 		Omit<Service, 'id' | 'created_at' | 'created_by' | 'patch_test_duration_hours'>
@@ -563,18 +565,18 @@
 				</div>
 
 				<div class="space-y-2">
-					<label for="service-duration" class="text-sm font-medium">Duration (minutes) *</label>
-					<Input
+					<label for="service-duration" class="text-sm font-medium">Duration *</label>
+					<select
 						id="service-duration"
-						type="number"
-						inputmode="numeric"
-						min="1"
-						step="1"
-						placeholder="60"
 						bind:value={newService.duration_minutes}
 						onblur={validateDurationField}
-						class="w-full {serviceErrors.duration_minutes ? 'border-red-500' : ''}"
-					/>
+						class="flex h-10 w-full rounded-md border border-input bg-background px-3 py-2 text-sm ring-offset-background focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 {serviceErrors.duration_minutes ? 'border-red-500' : ''}"
+					>
+						<option value={0}>Select...</option>
+						{#each durationOptions as mins (mins)}
+							<option value={mins}>{mins} min{mins >= 60 ? ` (${Math.floor(mins / 60)}h${mins % 60 > 0 ? ` ${mins % 60}m` : ''})` : ''}</option>
+						{/each}
+					</select>
 					{#if serviceErrors.duration_minutes}
 						<p class="text-sm text-red-600">{serviceErrors.duration_minutes}</p>
 					{/if}