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/HeapConvertDialog.svelte

@@ -14,7 +14,8 @@
 	import { Dialog } from 'bits-ui';
 	import { createMutation, createQuery, useQueryClient } from '@tanstack/svelte-query';
 	import { toast } from 'svelte-sonner';
-	import { FolderInput, Loader2 } from 'lucide-svelte';
+	import { FolderInput, FolderOpen, Loader2 } from 'lucide-svelte';
+	import { EmptyState, InlineLoader } from '$lib/components/feedback';
 	import {
 		convertHeap,
 		listFolders,
@@ -153,11 +154,14 @@
 				</div>
 				<div class="max-h-[200px] overflow-y-auto">
 					{#if foldersQuery.isPending}
-						<p class="px-2 py-1 text-[11px] text-muted-foreground">Loading folders…</p>
+						<InlineLoader size="sm" label="Loading folders…" />
 					{:else if (foldersQuery.data ?? []).length === 0}
-						<p class="px-2 py-1 text-[11px] text-muted-foreground">
-							No folders. Create one from the sidebar first.
-						</p>
+						<EmptyState
+							size="compact"
+							icon={FolderOpen}
+							title="No folders"
+							description="Create one from the sidebar first."
+						/>
 					{:else}
 						<!-- Root row: lets the user drop the heap directly into
 						     originals/ without picking a subfolder. The empty