feat(photos): full EXIF metadata extraction, backfill and info panel

- backend: switch EXIF parser to dsoprea/go-exif/v3 (all recognised tags, numeric normalization); store in photos.exif jsonb (migration 000003); add storage.Get and cmd/backfill-exif to backfill existing photos from S3 originals
- frontend: info panel renders all EXIF attributes with RU labels, enum translation and units (1/N, f/N, mm, EV); service tags hidden
- viewer: remove make-cover action (cover managed from panel only), icon-only download
- openspec: sync lightroom-workspace-ui artifacts (EXIF, cover-from-panel) and add plan for configurable info attributes/labels stored in user profile

frontend/src/lib/components/Viewer.svelte

@@ -7,24 +7,13 @@
 	interface Props {
 		photos: Photo[];
 		index: number;
-		canEdit?: boolean;
 		canDelete?: boolean;
 		onClose: () => void;
 		onIndexChange: (index: number) => void;
-		onMakeCover?: (photo: Photo) => void;
 		onDelete?: (photo: Photo) => void;
 	}
 
-	let {
-		photos,
-		index,
-		canEdit = false,
-		canDelete = false,
-		onClose,
-		onIndexChange,
-		onMakeCover,
-		onDelete
-	}: Props = $props();
+	let { photos, index, canDelete = false, onClose, onIndexChange, onDelete }: Props = $props();
 
 	let fresh = $state<Photo | null>(null);
 	let touchX = 0;
@@ -398,21 +387,16 @@
 			>
 				<Icon name={isFullscreen ? 'fullscreen_exit' : 'fullscreen'} />
 			</button>
-			{#if canEdit}
-				<button
-					type="button"
-					class={btn}
-					title="Сделать обложкой"
-					onclick={() => current && onMakeCover?.(current)}
-				>
-					<Icon name="wallpaper" class="size-4" />
-					<span class="hidden sm:inline">Обложка</span>
-				</button>
-			{/if}
 			{#if fresh?.download_url}
-				<a href={fresh.download_url} class={btn} target="_blank" rel="noreferrer">
+				<a
+					href={fresh.download_url}
+					class={btn}
+					target="_blank"
+					rel="noreferrer"
+					aria-label="Скачать"
+					title="Скачать"
+				>
 					<Icon name="download" class="size-4" />
-					<span class="hidden sm:inline">Скачать</span>
 				</a>
 			{/if}
 			{#if canDelete}