Fix a11y label associations across components

- Add for/id attributes to associate labels with form controls in PipelinePanel
- Add for/id for pipeline select in +page.svelte
- Change Device label to span since DeviceSelector has its own internal label

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/routes/+page.svelte

@@ -399,18 +399,19 @@
 			<!-- Controls bar -->
 		<div class="flex flex-col sm:flex-row sm:items-end justify-between gap-4 mb-6">
 			<div class="flex-1 max-w-xs">
-				<label class="block text-xs font-medium text-grey-500 uppercase tracking-wide mb-1.5">
+				<span class="block text-xs font-medium text-grey-500 uppercase tracking-wide mb-1.5">
 					Device
-				</label>
+				</span>
 				<DeviceSelector onCustomClick={openCustomModal} />
 			</div>
 
 			<div class="w-full sm:w-auto sm:max-w-xs">
-				<label class="block text-xs font-medium text-grey-500 uppercase tracking-wide mb-1.5">
+				<label for="pipeline-select" class="block text-xs font-medium text-grey-500 uppercase tracking-wide mb-1.5">
 					Pipeline
 				</label>
 				<div class="flex items-center gap-2">
 					<select
+						id="pipeline-select"
 						class="
 							flex-1 px-3 py-2
 							bg-white text-ink text-sm