web: unify empty + loading states behind EmptyState/InlineLoader

Replaces ad-hoc "Loading…" text and bare empty messages with two
shared feedback primitives that carry subtle lucide icons, consistent
muted-foreground/destructive tones, and a11y signaling (role=status,
aria-busy, role=alert on destructive empties). Loading copy gains
context ("Loading photos/folders/heaps/metadata…") and the right-
sidebar idle state moves from a "ⓘ" glyph to a MousePointerClick
icon. SkeletonGrid stays as the initial-grid loader.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/src/lib/components/layout/LeftSidebar.svelte

@@ -55,7 +55,9 @@
 		Copy,
 		Download,
 		FolderInput,
+		FolderOpen,
 		FolderPlus,
+		Layers,
 		LogOut,
 		Moon,
 		Pencil,
@@ -63,6 +65,7 @@
 		Sun,
 		Trash2
 	} from 'lucide-svelte';
+	import { EmptyState, InlineLoader } from '$lib/components/feedback';
 
 	const qc = useQueryClient();
 
@@ -757,9 +760,9 @@
 			</div>
 		</div>
 		{#if foldersQuery.isPending}
-			<p class="px-2 text-[11px] text-muted-foreground">Loading…</p>
+			<InlineLoader size="sm" label="Loading folders…" />
 		{:else if !hasSubfolders}
-			<p class="mt-1 px-2 text-[11px] text-muted-foreground">No subfolders.</p>
+			<EmptyState size="compact" icon={FolderOpen} title="No subfolders" />
 		{:else if rootExpanded}
 			<!--
 				depth=1 visually nests the top-level subfolders one indent
@@ -795,11 +798,11 @@
 		</div>
 
 		{#if heapsQuery.isPending}
-			<p class="px-2 text-[11px] text-muted-foreground">Loading…</p>
+			<InlineLoader size="sm" label="Loading heaps…" />
 		{:else if heapsQuery.isError}
-			<p class="px-2 text-[11px] text-destructive">Failed to load heaps</p>
+			<EmptyState size="compact" tone="destructive" title="Failed to load heaps" />
 		{:else if (heapsQuery.data ?? []).length === 0}
-			<p class="px-2 text-[11px] text-muted-foreground">No heaps yet.</p>
+			<EmptyState size="compact" icon={Layers} title="No heaps yet" />
 		{:else}
 			<ul>
 				{#each heapsQuery.data ?? [] as heap (heap.UID)}