feat: lightroom-style workspace UI with album covers

Backend:
- expose cover thumbnail URL on album responses (LEFT JOIN + presign)
- auto-assign cover only when empty; FK cover_photo_id -> photos ON DELETE SET NULL
- add photos_count / members_count to album responses; cover repo test

Frontend:
- split layouts into (app) shell (resizable rail + contextual panel) and (public)
- album rail + create-album dialog; album panel with cover picker / make-cover
- photo viewer route with filmstrip, replacing lightbox; share reuses it
- grid density slider, toolbar + drag-and-drop upload, dark graphite default

OpenSpec: add lightroom-workspace-ui change (proposal, design, specs, tasks)

frontend/src/lib/components/AlbumRail.svelte

@@ -0,0 +1,78 @@
+<script lang="ts">
+	import { page } from '$app/stores';
+	import { goto } from '$app/navigation';
+	import Icon from './Icon.svelte';
+	import CreateAlbumDialog from './CreateAlbumDialog.svelte';
+	import { albums } from '$lib/stores/albums.svelte';
+	import { auth } from '$lib/stores/auth.svelte';
+
+	const activeId = $derived($page.params.id ?? '');
+	let creating = $state(false);
+
+	$effect(() => {
+		if (auth.isAuthenticated && !albums.loaded) albums.load();
+	});
+</script>
+
+<div class="flex h-full flex-col">
+	<div class="border-border flex items-center justify-between border-b px-3 py-2">
+		<span class="text-text-muted text-xs font-semibold tracking-wide uppercase">Альбомы</span>
+		{#if auth.isAuthenticated}
+			<button
+				type="button"
+				class="text-text-muted hover:bg-bg-muted hover:text-text inline-flex items-center justify-center rounded-md p-1"
+				aria-label="Новый альбом"
+				title="Новый альбом"
+				onclick={() => (creating = true)}
+			>
+				<Icon name="add" class="size-4" />
+			</button>
+		{/if}
+	</div>
+
+	{#if !auth.isAuthenticated}
+		<p class="text-text-subtle p-3 text-sm">Войдите, чтобы видеть альбомы.</p>
+	{:else if albums.loading && albums.list.length === 0}
+		<p class="text-text-subtle p-3 text-sm">Загрузка…</p>
+	{:else if albums.list.length === 0}
+		<p class="text-text-subtle p-3 text-sm">Альбомов пока нет.</p>
+	{:else}
+		<ul class="flex-1 space-y-0.5 overflow-y-auto p-2">
+			{#each albums.list as album (album.id)}
+				<li>
+					<a
+						href="/albums/{album.id}"
+						class="flex items-center gap-2.5 rounded-md px-2 py-1.5 text-sm transition-colors {album.id ===
+						activeId
+							? 'bg-bg-muted text-text'
+							: 'text-text-muted hover:bg-bg-muted hover:text-text'}"
+						aria-current={album.id === activeId ? 'page' : undefined}
+					>
+						<span
+							class="bg-bg-muted border-border flex size-9 shrink-0 items-center justify-center overflow-hidden rounded border"
+						>
+							{#if album.cover_thumb_url}
+								<img
+									src={album.cover_thumb_url}
+									alt=""
+									class="h-full w-full object-cover"
+									loading="lazy"
+								/>
+							{:else}
+								<Icon name="image" class="size-4 text-text-subtle" />
+							{/if}
+						</span>
+						<span class="truncate">{album.title}</span>
+					</a>
+				</li>
+			{/each}
+		</ul>
+	{/if}
+
+	{#if creating}
+		<CreateAlbumDialog
+			onClose={() => (creating = false)}
+			onCreated={(album) => goto(`/albums/${album.id}`)}
+		/>
+	{/if}
+</div>