feat(photos): fix trash permanent delete and add empty trash

Permanently deleting a photo whose album was deleted failed because
authorization resolved through the album. Fall back to uploader
ownership when the photo is albumless. Add a bulk DELETE /trash that
removes every trashed photo the caller may delete (uncapped listing)
and returns the deleted count, with an «Очистить корзину» action on the
trash screen.

frontend/src/routes/(app)/trash/+page.svelte

@@ -4,6 +4,7 @@
 	import { portal } from '$lib/actions/portal';
 	import { photosApi, ApiError } from '$lib/api';
 	import { albums } from '$lib/stores/albums.svelte';
+	import { trash } from '$lib/stores/trash.svelte';
 	import type { Photo } from '$lib/types';
 
 	let photos = $state<Photo[]>([]);
@@ -12,6 +13,9 @@
 	let pending = $state<Photo | null>(null);
 	let busy = $state(false);
 
+	let confirmingEmpty = $state(false);
+	let emptyBusy = $state(false);
+
 	let restoring = $state<Photo | null>(null);
 	let targetId = $state('');
 	let createNew = $state(false);
@@ -92,12 +96,37 @@
 			busy = false;
 		}
 	}
+
+	async function emptyAll() {
+		if (emptyBusy) return;
+		emptyBusy = true;
+		try {
+			await photosApi.emptyTrash();
+			await load();
+			await trash.load();
+			confirmingEmpty = false;
+		} catch (e) {
+			error = (e as Error).message;
+		} finally {
+			emptyBusy = false;
+		}
+	}
 </script>
 
 <div class="p-4 sm:p-6">
 	<div class="mb-4 flex items-center gap-2">
 		<Icon name="delete" class="size-5 text-text-muted" />
 		<h1 class="text-xl font-semibold">Корзина</h1>
+		{#if photos.length > 0}
+			<button
+				type="button"
+				class="border-border text-danger hover:bg-bg-muted ml-auto inline-flex items-center gap-1.5 rounded-md border px-3 py-1.5 text-sm"
+				onclick={() => (confirmingEmpty = true)}
+			>
+				<Icon name="delete_forever" class="size-4" />
+				Очистить корзину
+			</button>
+		{/if}
 	</div>
 
 	{#if error}<p class="text-danger mb-3 text-sm">{error}</p>{/if}
@@ -166,6 +195,17 @@
 	/>
 {/if}
 
+{#if confirmingEmpty}
+	<ConfirmDialog
+		title="Очистить корзину?"
+		message="Все доступные вам для удаления элементы корзины будут удалены без возможности восстановления. Файлы хранилища удаляются, если на них нет ссылок в других альбомах."
+		confirmLabel="Очистить"
+		busy={emptyBusy}
+		onConfirm={emptyAll}
+		onClose={() => (confirmingEmpty = false)}
+	/>
+{/if}
+
 {#if restoring}
 	<div
 		use:portal