feat: photo rename and viewer delete with confirmation

Backend:
- add PATCH /api/photos/:id to rename original_filename (uploader/owner/admin)
- emit photo.updated SSE event

Frontend:
- inline filename editor in the right panel
- viewer: back button (arrow_back) on the left, delete on the right
- delete confirmed via a modal dialog; filmstrip updates after deletion

frontend/src/lib/components/Viewer.svelte

@@ -7,12 +7,23 @@
 		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, onClose, onIndexChange, onMakeCover }: Props = $props();
+	let {
+		photos,
+		index,
+		canEdit = false,
+		canDelete = false,
+		onClose,
+		onIndexChange,
+		onMakeCover,
+		onDelete
+	}: Props = $props();
 
 	let fresh = $state<Photo | null>(null);
 	let touchX = 0;
@@ -52,13 +63,20 @@
 
 	const btn =
 		'border-border text-text hover:bg-bg-muted inline-flex items-center gap-1.5 rounded-lg border px-3 py-1.5 text-sm';
+	const dangerBtn =
+		'border-border text-danger hover:bg-bg-muted inline-flex items-center gap-1.5 rounded-lg border px-3 py-1.5 text-sm';
 </script>
 
 <svelte:window onkeydown={onKey} />
 
 <div class="flex h-full flex-col">
 	<div class="border-border flex shrink-0 items-center justify-between gap-2 border-b px-3 py-2">
-		<span class="text-text-muted text-sm">{index + 1} / {photos.length}</span>
+		<div class="flex items-center gap-2">
+			<button type="button" class={btn} aria-label="Назад" title="Назад" onclick={onClose}>
+				<Icon name="arrow_back" />
+			</button>
+			<span class="text-text-muted text-sm">{index + 1} / {photos.length}</span>
+		</div>
 		<div class="flex items-center gap-2">
 			{#if canEdit}
 				<button
@@ -77,9 +95,17 @@
 					<span class="hidden sm:inline">Скачать</span>
 				</a>
 			{/if}
-			<button type="button" class={btn} aria-label="Закрыть" title="Закрыть" onclick={onClose}>
-				<Icon name="close" />
-			</button>
+			{#if canDelete}
+				<button
+					type="button"
+					class={dangerBtn}
+					aria-label="Удалить фото"
+					title="Удалить фото"
+					onclick={() => current && onDelete?.(current)}
+				>
+					<Icon name="delete" class="size-4" />
+				</button>
+			{/if}
 		</div>
 	</div>