feat(web): keyboard rating/color marks, search focus, shortcuts overlay

Lightroom-style keys in grid+preview: 0-5 rating (re-key toggles),
6-9 color labels, optimistic marks cache patch with rollback. / focuses
the search box, ? opens a new shortcut-reference overlay that inertly
swallows other keys while open.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

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

@@ -0,0 +1,120 @@
+<!--
+	Keyboard-shortcut reference overlay, opened with `?` (and the toolbar
+	help affordance). Read-only: gridKeyNav swallows every key except
+	Esc / ? while it's up, so nothing here can fire the actions it lists.
+-->
+<script lang="ts">
+	import { closeShortcuts, view } from '$lib/stores/view.svelte';
+	import { X } from 'lucide-svelte';
+
+	interface Row {
+		keys: string[];
+		desc: string;
+	}
+	interface Group {
+		title: string;
+		rows: Row[];
+	}
+
+	const GROUPS: Group[] = [
+		{
+			title: 'Navigate',
+			rows: [
+				{ keys: ['↑', '↓', '←', '→'], desc: 'Move focus in the grid' },
+				{ keys: ['Shift', '+', 'Arrows'], desc: 'Extend selection' },
+				{ keys: ['Space'], desc: 'Open / close preview' },
+				{ keys: ['Esc'], desc: 'Collapse selection, then clear' },
+				{ keys: ['/'], desc: 'Focus search' },
+				{ keys: ['⌘', 'A'], desc: 'Select all visible' },
+				{ keys: ['⌘', 'K'], desc: 'Command palette' }
+			]
+		},
+		{
+			title: 'Rate & label',
+			rows: [
+				{ keys: ['1', '…', '5'], desc: 'Set rating (re-key to clear)' },
+				{ keys: ['0'], desc: 'Clear rating' },
+				{ keys: ['6', '7', '8', '9'], desc: 'Color label: red / yellow / green / blue' },
+				{ keys: ['F'], desc: 'Toggle favorite' }
+			]
+		},
+		{
+			title: 'Act',
+			rows: [
+				{ keys: ['X'], desc: 'Archive (Delete in Archive view)' },
+				{ keys: ['U'], desc: 'Restore from archive' },
+				{ keys: ['S'], desc: 'Keep (review) · add to heap' },
+				{ keys: ['S', 'then', '1–9'], desc: 'Add to heap N' },
+				{ keys: ['A'], desc: 'Accept date & keep (EXIF review)' },
+				{ keys: ['M'], desc: 'Move to folder' },
+				{ keys: ['⌘', 'Z'], desc: 'Undo last action' }
+			]
+		},
+		{
+			title: 'Panels',
+			rows: [
+				{ keys: ['B'], desc: 'Toggle left sidebar' },
+				{ keys: ['Tab'], desc: 'Toggle left sidebar' },
+				{ keys: ['I'], desc: 'Toggle info sidebar' },
+				{ keys: ['?'], desc: 'This overlay' }
+			]
+		}
+	];
+</script>
+
+{#if view.shortcutsOpen}
+	<!-- svelte-ignore a11y_click_events_have_key_events a11y_no_static_element_interactions -->
+	<div
+		class="fixed inset-0 z-[70] flex items-center justify-center bg-black/50 backdrop-blur-sm"
+		onclick={(e) => {
+			if (e.target === e.currentTarget) closeShortcuts();
+		}}
+	>
+		<div
+			role="dialog"
+			aria-modal="true"
+			aria-label="Keyboard shortcuts"
+			class="max-h-[85vh] w-[min(680px,92vw)] overflow-y-auto rounded-lg border border-border bg-popover p-5 text-popover-foreground shadow-xl"
+		>
+			<div class="mb-4 flex items-center justify-between">
+				<h2 class="text-sm font-semibold">Keyboard shortcuts</h2>
+				<button
+					class="rounded p-1 text-muted-foreground hover:bg-accent hover:text-foreground"
+					onclick={closeShortcuts}
+					aria-label="Close"
+				>
+					<X class="h-4 w-4" />
+				</button>
+			</div>
+			<div class="grid gap-x-8 gap-y-4 sm:grid-cols-2">
+				{#each GROUPS as group (group.title)}
+					<section>
+						<h3 class="mb-1.5 text-[10px] font-medium uppercase tracking-wide text-muted-foreground">
+							{group.title}
+						</h3>
+						<dl class="space-y-1">
+							{#each group.rows as row (row.desc)}
+								<div class="flex items-center justify-between gap-3 text-xs">
+									<dt class="text-muted-foreground">{row.desc}</dt>
+									<dd class="flex shrink-0 items-center gap-0.5">
+										{#each row.keys as k (k)}
+											{#if k === 'then' || k === '+' || k === '…'}
+												<span class="px-0.5 text-[10px] text-muted-foreground">{k}</span>
+											{:else}
+												<kbd
+													class="rounded border border-border bg-muted px-1.5 py-0.5 font-mono text-[10px] leading-none"
+												>
+													{k}
+												</kbd>
+											{/if}
+										{/each}
+									</dd>
+								</div>
+							{/each}
+						</dl>
+					</section>
+				{/each}
+			</div>
+		</div>
+	</div>
+{/if}