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/CreateAlbumDialog.svelte

@@ -0,0 +1,88 @@
+<script lang="ts">
+	import Icon from './Icon.svelte';
+	import { albums } from '$lib/stores/albums.svelte';
+	import type { Album } from '$lib/types';
+
+	interface Props {
+		onClose: () => void;
+		onCreated?: (album: Album) => void;
+	}
+
+	let { onClose, onCreated }: Props = $props();
+
+	let title = $state('');
+	let busy = $state(false);
+	let error = $state('');
+
+	async function submit(ev: Event) {
+		ev.preventDefault();
+		if (!title.trim() || busy) return;
+		busy = true;
+		error = '';
+		try {
+			const album = await albums.create(title.trim());
+			onCreated?.(album);
+			onClose();
+		} catch (e) {
+			error = (e as Error).message;
+		} finally {
+			busy = false;
+		}
+	}
+
+	function onKey(ev: KeyboardEvent) {
+		if (ev.key === 'Escape') onClose();
+	}
+
+	function autofocus(node: HTMLInputElement) {
+		node.focus();
+	}
+</script>
+
+<svelte:window onkeydown={onKey} />
+
+<div
+	class="fixed inset-0 z-50 flex items-center justify-center bg-black/50 p-4"
+	role="dialog"
+	aria-modal="true"
+	aria-label="Новый альбом"
+	tabindex="-1"
+	onclick={(e) => {
+		if (e.target === e.currentTarget) onClose();
+	}}
+	onkeydown={onKey}
+>
+	<form
+		class="border-border bg-bg-elevated w-full max-w-sm space-y-4 rounded-xl border p-5"
+		onsubmit={submit}
+	>
+		<h2 class="text-lg font-semibold">Новый альбом</h2>
+		<label class="block">
+			<span class="text-text-muted mb-1 block text-sm">Название</span>
+			<input
+				bind:value={title}
+				use:autofocus
+				class="border-border bg-bg text-text w-full rounded-lg border px-3 py-2"
+				placeholder="Например, Отпуск"
+			/>
+		</label>
+		{#if error}<p class="text-danger text-sm">{error}</p>{/if}
+		<div class="flex justify-end gap-2">
+			<button
+				type="button"
+				class="border-border text-text rounded-lg border px-4 py-2 text-sm"
+				onclick={onClose}
+			>
+				Отмена
+			</button>
+			<button
+				type="submit"
+				disabled={busy || !title.trim()}
+				class="bg-primary text-primary-fg inline-flex items-center gap-1.5 rounded-lg px-4 py-2 text-sm disabled:opacity-50"
+			>
+				<Icon name="add" class="size-4" />
+				{busy ? 'Создание…' : 'Создать'}
+			</button>
+		</div>
+	</form>
+</div>