Remove background picker from board settings

Background customization is available in the Branding section.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/components/BoardSettingsModal.svelte

@@ -3,7 +3,6 @@
 	import { trapFocus } from '$lib/utils/focus-trap.js';
 	import { api } from '$lib/utils/api.js';
 	import { toast } from '$lib/stores/toasts.svelte.js';
-	import BoardBackgroundPicker from './BoardBackgroundPicker.svelte';
 
 	type Props = {
 		board: any;
@@ -138,12 +137,6 @@
 				</div>
 			{/if}
 
-			<!-- Background -->
-			<div>
-				<span class="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">Background</span>
-				<BoardBackgroundPicker boardId={board.id} currentBackground={board.background} />
-			</div>
-
 			<!-- Save -->
 			<button
 				onclick={save}