fix(redesign): a11y, mobile, perf polish for production push

Comprehensive pre-production sweep across the Aurora redesign — drives
svelte-check to 0 errors / 0 warnings (was 61) without changing visual
intent. Highlights:

- Mobile: hero title shrinks at 480px, signal-list stacks timestamp
  under sentence below 640px, sidebar icon buttons bumped to 40x40
- Light theme: muted-foreground darkened to #3a3560 to clear WCAG AA
  on glass surfaces and the modal close button
- Perf: topbar backdrop-filter 28→14px, mobile-more sheet 28→12px to
  cut concurrent blur layers on mid-tier mobile
- a11y: prefers-reduced-motion mute for aurora drift / pulses /
  shimmer / stagger; aria-label on every icon-only button;
  aria-describedby on Hint; combobox/listbox/aria-activedescendant on
  SearchPalette; modal dialog tabindex; 47 label-without-control
  warnings across 14 form pages cleaned up via for=/id= or label→div
- Dashboard derived state split into topology- vs status-bound layers
  so polling no longer re-runs the full provider/wires computation
- Mobile bottom nav derived from baseNavEntries by key lookup so
  adding a top-level nav entry keeps the two trees in sync
- Bug: template-configs page now respects the global provider filter
  for both the count meter and the type pill (was reading the
  unfiltered cache)
- Misc: portal EventChart tooltip and switch its swatches to Aurora
  tokens; CollapsibleSlot warning state uses warning-fg/-bg tokens
  instead of #d97706; Hint z-index 99999→9999; element refs across
  Modal/EntitySelect/MultiEntitySelect/SearchPalette/IconGridSelect/
  Hint/targets converted to \$state for reactivity; 4 dead
  .topbar-cta selectors removed

frontend/src/routes/targets/TargetForm.svelte

@@ -79,7 +79,7 @@
 	<form onsubmit={onsave} class="space-y-4">
 		{#if !activeType}
 		<div>
-			<label class="block text-sm font-medium mb-1">{t('targets.type')}</label>
+			<div class="block text-sm font-medium mb-1">{t('targets.type')}</div>
 			<IconGridSelect items={typeGridItems} bind:value={formType} columns={4} />
 		</div>
 		{/if}
@@ -92,7 +92,7 @@
 		</div>
 		{#if formType === 'telegram'}
 			<div>
-				<label class="block text-sm font-medium mb-1">{t('telegramBot.selectBot')}</label>
+				<div class="block text-sm font-medium mb-1">{t('telegramBot.selectBot')}</div>
 				<EntitySelect items={telegramBotItems} bind:value={form.bot_id} placeholder={t('telegramBot.selectBot')} />
 				{#if telegramBotCount === 0}
 					<p class="text-xs text-[var(--color-muted-foreground)] mt-1">{t('telegramBot.noBots')} <a href="/bots?tab=telegram" class="underline">→</a></p>
@@ -124,7 +124,7 @@
 						<input id="tgt-maxsize" type="number" bind:value={form.max_asset_size} min="1" max="50" class="w-full px-2 py-1 border border-[var(--color-border)] rounded-md text-sm bg-[var(--color-background)]" />
 					</div>
 					<div class="col-span-2">
-						<label class="block text-xs mb-1">{t('targets.chatAction')}</label>
+						<div class="block text-xs mb-1">{t('targets.chatAction')}</div>
 						<IconGridSelect items={chatActionItems} bind:value={form.chat_action} columns={4} compact />
 					</div>
 					<label class="flex items-center gap-2 text-sm col-span-2"><input type="checkbox" bind:checked={form.disable_url_preview} /> {t('targets.disableUrlPreview')}</label>
@@ -151,7 +151,7 @@
 			</div>
 		{:else if formType === 'email'}
 			<div>
-				<label class="block text-sm font-medium mb-1">{t('targets.selectEmailBot')}</label>
+				<div class="block text-sm font-medium mb-1">{t('targets.selectEmailBot')}</div>
 				<EntitySelect items={emailBotItems} bind:value={form.email_bot_id} placeholder={t('targets.selectEmailBot')} />
 				{#if emailBotCount === 0}
 					<p class="text-xs text-[var(--color-muted-foreground)] mt-1">{t('emailBot.noBots')} <a href="/bots?tab=email" class="underline">→</a></p>
@@ -159,7 +159,7 @@
 			</div>
 		{:else if formType === 'matrix'}
 			<div>
-				<label class="block text-sm font-medium mb-1">{t('targets.selectMatrixBot')}</label>
+				<div class="block text-sm font-medium mb-1">{t('targets.selectMatrixBot')}</div>
 				<EntitySelect items={matrixBotItems} bind:value={form.matrix_bot_id} placeholder={t('targets.selectMatrixBot')} />
 				{#if matrixBotCount === 0}
 					<p class="text-xs text-[var(--color-muted-foreground)] mt-1">{t('matrixBot.noBots')} <a href="/bots?tab=matrix" class="underline">→</a></p>
@@ -168,7 +168,7 @@
 		{:else if formType === 'broadcast'}
 			{@const childIds = (form.child_target_ids || []).map(String)}
 			<div>
-				<label class="block text-sm font-medium mb-1">{t('targets.selectChildTargets')}</label>
+				<div class="block text-sm font-medium mb-1">{t('targets.selectChildTargets')}</div>
 				<MultiEntitySelect
 					items={broadcastChildItems?.map(i => ({ value: String(i.value), label: i.label, icon: i.icon, desc: i.desc })) ?? []}
 					values={childIds}